Class 8 Science

KSEEB Solutions for Class 8 Science Chapter 2 Microorganisms Friend And Foe Points To Remember

Microorganisms: Living organisms that cannot be seen with the naked eye.
Types: Bacteria, Fungi, Protozoa, Algae, viruses.

Friendly microorganisms:
1. Making curd and bread
2. production of alcohol and wine
3. production of vaccines and antibiotics
4. increases soil fertility
5. cleaning of the environment.

Harmful microorganisms:
1. Diseases like cholera, TB, Typhoid, Measles, and Malaria are caused by micro-organisms in Humans.
2. Diseases like anthrax and foot and mouth disease are caused by bacteria and viruses in cattle.
3. Diseases like citrus canker, rust of wheat, and yellow vein mosaic of okra in plants.
3. Foods are spoilt by microorganisms.

Food preservation:
1. Chemical method
2. By sugar
3. Heat and cold treatments
4. By common salt
5. By oil and vinegar
6. Storage and packing

Class 8 Science KSEEB Microorganisms Friend and Foe Notes 

Microorganisms Friend And Foe Ncert Textbook Exercises

Question 1. Fill in the blanks.
(1)Microorganisms can be seen with the help of a
(2) Blue-green algae fix directly from the air to enhance the fertility of the soil.
(3)Alcohol is produced with the help of
(4)Cholera is caused by
Answer:
(1) microscope
(2) nitrogen
(3) yeast
(4) bacteria

Question 2.Tick the correct answer:
1)Yeast is used in the production of
(1)sugar
(2) Alcohol
(3)hydrochloric acid
(4) oxygen

2)Which of the following is an antibiotic?
(1)Sodium bicarbonate
(2) Streptomycin
(3) Alcohol
(4) yeast

3)Carrier of malaria-causing protozoa is
(1)female Anopheles mosquito
(2)cockroach
(3)housefly
(4)butterfly

4)The most common carrier of communicable diseases is
(1)ant
(2) housefly
(3) dragonfly
(4) spider

5)The bread or idli dough rises because of
(1) heat
(2) housefly
(3) growth of yeast cells
(4) kneading

(6)The process of conversion of sugar into alcohol is called
(1) nitrogen fixation
(2) molding
(3) fermentation
(4) infection
Answer: 1) – (2); 2) – (2); 3) – (1); 4) – (2), (5) – (3); 6) – (3)

Question 3. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: Microorganisms cannot be seen by the naked eye because they are very small. They can be seen by using a microscope.

Question 4. What are the major groups of microorganisms?
Answer: Major groups of microorganisms is as follows:
1. Bacteria
2. Fungi
3. Protozoans
4. Algae
5. Viruses.

Question 5. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer: Rhizobium.

Question 6. Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Uses of microorganisms are as follows :

1. They are helpful in cleaning up the environment.
2. Lactobacillus promotes the formation of curd.
3. Bacteria are involved in the making of cheese
4. Bacteria and yeast are helpful for the fermentation of rice idlis and dosa batter.
5. Use of yeast in the baking industry for making bread, pastries, and cakes.
6. Large-scale production of alcohol, wine, and vinegar.
7. Microorganisms are helpful in producing vaccines against the disease.
8. Antibiotics are produced from bacteria and fungi
9. Some bacteria are able to fix nitrogen and increase soil fertility.
10. Microorganisms decompose dead and decaying organic matter of plants and animals.

Question 7. Write a short paragraph on the harmful effects of microorganisms.
Answer: Microorganisms cause diseases in plants and animals,
Example: Cholera in humans is caused by bacteria called Vibrio cholera. In animals, the virus causes foot and mouth diseases. Microorganisms spoil the food by decomposing the food material. Some microorganisms spoil leather and clothes. Microorganisms are responsible for food poisoning.

KSEEB Class 8 Science Solutions For Microorganisms Friend And Foe 

Question 8. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer:

Chemical agents that kill or stop the growth of disease-causing microorganisms are called antibiotic

Antibiotics should be taken only on the advice of a qualified doctor. Also, one must complete the course prescribed by the doctor.

Microorganisms Friend And Foe Activities

Question 1. Collect some moist soil from the field in a beaker and add water to it. After the soil particles have settled down, observe a drop of water from the beaker under a microscope. What do you see?
Answer: It is observed that some tiny organisms are moving around.

Question 2. Take a few drops of water from a pond. Spread on a glass slide and observe through a microscope.
Answer: It is observed that some tiny organisms are moving around.
Question 3. Take 1/2 kg flour (atta or maida), add some sugar, and mix with warm water. Add a small amount of yeast powder and knead to make a soft dough. What do you observe after two hours? Did you find the dough rising?
Answer: It is observed that the dough begins to rise up in volume. Yeast reproduces rapidly and releases Co₂ during respiration. The stubble of this gas fills the dough and increases its volume.

Question 4. Take 500 ml. beaker filled up to 3/4 with water. Dissolve 2-3 teaspoons of sugar in it. Add half a spoon of yeast powder to the sugar solution. Keep it covered in a warm place for 4-5 hours. Now smell the solution. Can you get a smell?

Answer: It is observed that the solution smell like alcohol. This process of conversion of sugar into alcohol is known as fermentation.

Question 5. Take two pots and fill each pot half with soil. Mark them A and B. Put plant waste in pot A and things like polythene bags, empty glass bottles, and broken plastic toys in pot B. Put the pots aside. Observe them after 3-4 weeks.
Answer: It is observed that plant waste in pot A has been decomposed, whereas the polythene bags, empty glass bottles, and broken plastic toys in pot B did not undergo such changes.

Microorganisms Friend And Foe Additional Questions

Question 1. Riya’s grandmother always dries vegetables in the sun before pickling them. How does drying help vegetables?
Answer: Drying vegetables help to remove water, which is necessary for microbial growth. So drying helps in preserving them.

Question 2. On a pack of fruit juice, it is printed “IF THE PACKET IS PUFFED DO NOT BUY”. Give reasons.
Answer: Because packed juices may be contaminated by yeast which causes fermentation and makes them unfit for consumption.

Question 3. Name any two antibiotics.
Answer: Streptomycin and tetracycline.

Question 4. Name the scientist who discovered the vaccine for smallpox in 1798.
Answer: Edward Jenner

Question 5. What do you mean by communicable diseases?
Answer: The microbial diseases that can spread from an infected person to a healthy person by some agents like air, water, food, or physical contact are called communicable diseases.

Question 6. Write the name of a bacterium that helps in the formation of curd.
Answer: Lactobacillus

Question 7. Write the use of yeast.
Answer: Yeast is used in the production of alcohol, wine, beer, and other beverages.

Question 8. What are pathogens? Write another name for pathogens.
Answer: Disease-causing microorganisms are known as pathogens. They are also called germs.

Question 9. Define food preservation.
Answer: Food preservation is the method of preserving food from being spoiled by microbes.

Question 10. What is fermentation?
Answer: Fermentation is the process of conversion of food into alcohol.

Microorganisms Friend And Foe Class 8 KSEEB Questions And Answers 

Question 11. Define communicable diseases. Give some examples.
Answer: Communicable diseases are microbial diseases that can spread from an infected person to a healthy person through the air, water, or another physical contact; e.g., cholera, chicken pox, tuberculosis, common cold, etc.

Question 12. Give two examples of each of the following types of microorganisms:
(1)Algae
(2) Fungi
(3) Protozoa
Answer:
(1) Algae – Spirogyra, Chlamydomonas
(2)Fungi-Aspergillus, yeast
(3)Protozoa – Paramecium, Amoeba

Question 13.Unscramble the jumbled words underlined in the following statements
(1)Curbossulite is an air-borne disease caused by a bacterium.
(2)Xanrhat is a dangerous bacterial disease.
(3)Yeasts are used in the wine industry because of their property of meronettinaf.
(4)Cells of our body produce antidotes to fight pathogens.
(5)Aeeessrrwtip are added to food to prevent the growth of microorganisms.
Answer:
(1) Tuberculosis
(2)Anthrax
(3)Fermentation
(4)antibodies
(5)Preservatives

Multiple Choice Questions

Question 14. Which of the following reproduces only inside a host cell?
(1)Bacteria
(2) Virus
(3) Amoeba
(4) Fungus.
Answer:(2) Virus
Explanation: The virus is considered an intermediate between living and non-living. Outside a host-virus remains inactive. It can perform its life processes and reproduction only when it is inside a host cell.

Question 15. A disease in human beings caused by a virus is
(1)Typhoid
(2) Influenza
(3) Dysentery
(4) Cholera
Answer: (2) Influenza
Explanation:

Typhoid is caused by the bacteria Salmonella typhoid.

Dysentry is caused by an amoeba which is a protozoan.

Cholera is caused by Vibrio cholera bacteria.

Question 16. Pathogenic micro-organisms present in host cells are killed by medicines called
(1) Painkiller
(2) Antibodies
(3) Antibiotics
(4) Vaccines
Answer: (2) Antibiotics
Explanation:

Pain Killers give relief from pain.

Antibodies are produced by our immune system which acts and elicits a specific immune reaction.

Antibiotics that inhibit or kill certain bacteria.

Vaccines provide acquired immunity against a particular disease.

Question 17. The two micro-organisms which live in symbiotic association in lichens are
(1)Fungus and Protozoa
(2)Alga and Bacteria
(3)Bacteria and Protozoa
(4)Alga and Fungus
Answer: (4) Alga and Fungus

Question 18. The gas released during the preparation of bread is
(1)Oxygen
(2) Carbon dioxide
(3) Nitrogen
(4) Sulphur dioxide
Answer: (2) Carbon dioxide
Explanation: Carbon-di-oxide is released due to the fermentation process conducted by yeast. C02 causes the rising of the dough and makes the bread fluffy.

Question 19. The disease caused by a protozoan and spread by an insect is.
(1) Dengue
(2) Malaria
(3)Polio
(4) Measles
Answer: (2) Malaria
Explanation: Malaria is caused by a protozoan named Plasmodium vivax which is transmitted by mosquitos. Other options are viral diseases hence they are wrong answers.

Question 20. Paheli dug two pits, A and B, in her garden. In pit A, she put a polythene bag packed with some agricultural waste. In pit B, she dumped the same kind of a waste but without packing it in a polythene bag. She then covered both pits with soil. What did she observe after a month?
(1)Waste in pit A degraded faster than that in pit B.
(2)Waste in pit B degraded faster than that in pit A.
(3) Waste in both pits degraded almost equally.
(4)Waste in both pits did not degrade at all.
Answer: (2) Waste in pit B degraded faster than that in pit A.
Explanation: Waste in pit B degrades faster than waste in pit A because Polythene in pit B is open and receives oxygen for composting whereas polythene in closed in pit A and organisms don’t receive oxygen to compost the waste material in the polythene bag.

Question 21. Suggest a suitable word for each of the following statements.
(1)Chemicals added to food to prevent the growth of microorganisms.
(2)Nitrogen-fixing microorganisms present in the root nodules of legumes.
(3)The agent spreads pathogens from one place to another.
(4)Chemicals that kill or stop the growth of pathogens.
Answer: 1. Preservatives
2. Rhizobium
3. Carrier/ vector
4. Antibiotics

Question 22. Name the process in yeast that converts sugars into alcohol.
Answer: Fermentation is the process in yeast that converts sugars into alcohol.

Question 23.In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?
Answer: Blue-green-algae enriches Nitrogen in the soil.

Question 24. Why should we avoid standing close to a tuberculosis patient while he/she is coughing?
Answer: Tuberculosis can spread through the air when the infected person coughs. Hence we avoid standing close to a tuberculosis patient while he/she is coughing.

Question 25. Polio drops are not given to children suffering from diarrhea. Why?
Answer: If the children are suffering from diarrhea oral polio drops will get excreted due to frequent motions. Hence children with diarrhea are not given polio drops.

Question 26. Paheli watched her grandmother making mango pickles. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured. Can you help her understand why?
Answer: Oils prevent the attack of bacteria which will help preserve the pickle for a long period of time.

Explanation Of Microorganisms Friend And Foe In KSEEB Science 

Question 27. Classify the following into friendly and harmful microorganisms.
Answer:
Friendly

Yeast

Lactobacillus

Rhizobium

Harmful Microorganisms

Malarial parasite

Bread mold

Bacillus anthracis

Question 28. While returning from school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?
Answer: The probable reason is that the chaat was contaminated by pathogenic microbes due to unhygienic conditions near the shop or the utensil used for serving could have been contaminated.
The reason may be the contamination of food by pathogenic microbes. Contamination may be due to the unhygienic conditions near the shop or the utensil used to serve the chaat.

Question 29. What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?
Answer: Pooris and unused kneaded flour get spoiled due to microbial activity. Food gets fermented when kept open and it will be spoiled.

Question 30. (1) Name two diseases that are caused by the virus.
(2)Write one important characteristic of the virus.
Answer:
1. Polio, HIV
2. A virus can reproduce only when it is inside the host cell.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions for Class 8 Science Chapter 3 Synthetic Fibres And Plastics Points To Remember

Synthetic Fibres: Fibres artificially made by man.

Synthetic Fibres: They are made of very large units called polymers, (chemicals). Polymers are made up of many smaller units called monomers by the process of polymerisation.

Characteristics of synthetic fibres: dry up quickly, durable, less expensive, easy to maintain.

Types of synthetic fibres: Rayon, Nylon, Polyester, Acrylic.

Rayon was the first artificially manufactured fibre from wood pulp.

Coal and petroleum are raw materials to manufacture nylon.

Polyester has many ester units linked together

Acrylic is used as a substitute for wool

Plastics: Synthetic organic polymers that can be shaped when soft and later hardened to set to shape.

Characteristics of plastics: Non-reactive, light, strong durable, poor conductors of heat and electricity.

Types of plastics: Thermoplastics and thermosetting plastics

Thermoplastics: get deformed easily on heating. Examples: PVC, polyethene

Thermosetting plastics: cannot be bent easily. Example: Bakelite, melamine

Effect of plastics on the Environment: Non-bio-degradable, pollute the environment, and release poisonous fumes on burning.

Non-biodegradable – substances that cannot decay by the natural process of decomposers.

Class 8 Science KSEEB Synthetic Fibres And Plastics Notes 

Synthetic Fibres And Plastics Textbook Exercises

Question 1. Explain why some fibres are called synthetic.
Answer: Some fibres are called synthetic because they are made by man using chemicals. These are made of small units that join together to form long chains.

Question 2. Mark ( ✓ ) the correct answer :
Rayon is different from synthetic fibres because
(1)it has a silk-like appearance.
(2)it is obtained from wood pulp
(3)its fibres can also be woven like those of natural fibres
(4)none of the above.
Answer: (2)

Question 3. Fill in the blanks with appropriate words:
1)Synthetic fibres are also called______or______fibres.
2)Synthetic fibres are synthesised from a raw material called _____
3)Like synthetic fibres, plastic is also a________
Answer:
1)artificial, man-made
2)petrochemicals
3)polymer

Question 4. Give examples which indicate that nylon fibres are very strong.
Answer:

They are used for making parachutes and ropes for rock climbing.

They are used in making seat – belts, fishing nets, tyre cords, a string for sports rackets and musical instruments.

Question 5. Explain why plastic containers are favoured for storing food.
Answer: Plastic containers are favoured for storing food because

Plastics do not react with food stored in them.

Plastics are lightweight and strong

They are easy to handle and safe.

Question 6.Explain the difference between thermoplastic and thermosetting plastics
Answer: Thermoplastics

These plastics soften on heating and can be bent easily.

They do not lose their plasticity.
Examples: PVC, polyethene.
Thermosetting plastics

These plastics once moulded can’t be softened again.

They lose their plasticity
Example: Bakelite and melamine

Question 7. Explain why the following are made of thermosetting plastics.
1)Saucepan handles
2)Electric plugs/switches/plug boards
Answer:
(1) Since thermosetting plastics are bad conductors of heat and do not get heated up while cooking, they are used for making saucepan handles.
(2)Since thermosetting plastics are bad conductors of electricity and the electric current does not pass through such plastics, they are used for making electric plugs/switches/plugboards

Question 8. Categorise the materials of the following products into can be recycled and ‘cannot be recycled.
Telephone instruments, plastic toys, cooker handles, carry bags, ballpoint pens, plastic bowls, plastic covering on electrical wires, plastic chairs, and electrical switches.
Answer:
Can be recycled: Plastic toys, carry bags, plastic bowls, plastic covering on electrical wires, plastic chairs.
Cannot be recycled: Telephone instruments, cooker handles, ballpoint pens, electrical switches.

Question 9. Rana wants to buy shirts for summer should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.
Answer: He should buy cotton shirts. This is because cotton has more capacity, to hold moisture than synthetic clothes. In summer, we have extensive sweat which is easily soaked by cotton shirts and hence, cotton clothes are much better than clothes made from synthetic material.

Question 10. Give examples to show that plastics are non-corrosive in nature.
Answer:

Plastic containers do not react with items stored in them.

They do not get rusted when exposed to moisture and air.

They do not decompose when left in open for a long period.

Question 11. Should the handle and bristles of a toothbrush be made of the same material? Explain your answer.
Answer: No, the handle and bristles of a toothbrush should not be made of the same material. This is because our gums are soft and the bristles should be made of soft material so that it does not harm the gums. On the other hand, the handles should be made up of hard material so that they can give a firm grip.

KSEEB Class 8 Science Solutions For Synthetic Fibres And Plastics 

Question 12.‘Avoid plastics as far as possible comment on this advice.
Answer: Plastics must be avoided as far as possible. Materials made of plastics are non-biodegradable. The use of plastics had a bad effect on the environment. When the plastics are burnt, it releases a lot of poisonous fumes into the atmosphere causing air pollution. These plastic materials when eaten up by the animals (like cows) choke the- respiratory system. This can cause the death of these animals. The waste particle articles thrown here and there carelessly get into dirty water drains and sewers and block them. In a nutshell, plastics can be considered a threat to our environment.

Synthetic Fibres And Plastics Activities

Question 1. Take an iron stand with a clamp. Take a cotton thread of about 60 cm in length. Tie it to the clamp so that it hangs freely from it.

Answer: At the free end suspend a pan so that weight can be placed in it. Add weight one by one till the thread breaks. Note down the total weight required to break the thread. This weight indicates the strength of the fibre. Repeat the same activity with threads of wool, polyester, silk and nylon. Tabulate the data Arrange the threads in order of their increasing strength.

(Precaution: Note that all threads should be of the same length and most of the same thickness.)

Question 2. Take two cloth pieces of the same size, roughly half a metre square each. One of these should be from natural fibre. The other could be synthetic fibre. You can take the help of your parents in selecting these pieces. Soak the pieces in different mugs each containing the same amount of water. Take the pieces out of the containers after five minutes and spread them in the sun for a few minutes. Compare the volume of the water remaining in each container.
Answer: It is observed that the volume of water in the container in which natural fibre is soaked contains less water as compared to the container in which synthetic fibre is soaked. Thus, natural fibre absorbs more water as compared to synthetic fibre. When both the fibres were spread in the sun, it was observed that synthetic fibre took less time to dry than natural fibre.

Synthetic Fibres And Plastics Additional Questions

Question 1. Distinguish between natural and synthetic fibres.
Answer: Natural fibres

These fibres are naturally obtained from plants and animals. Ex: cotton, silk, etc Synthetic fibres

These fibres are made by men in factories.

Examples: Rayon, polyester, etc.

Question2.Cotton is a natural polymer. What is its chemical name?
Answer: Cellulose

Question 3. Terrycot is made by mixing two types of fibres. Write the names of the fibres.
Answer: Terylene and cotton

Question 4. What is PET?
Answer: Poly-Ethylene

Question 5. What is meant by the 4R’s principle?
Answer: Reduce, Reuse, Recycle and Recover

Question 6. Why should one never wear polyester clothes while working in the kitchen?
Answer: Polyester clothes are synthetic fibre and melt on heating. If the clothes catch fire, it can be disastrous, the fabric melts and sticks to the body. So, one should never wear synthetic clothes while working in the kitchen.

Question 7. Name some objects made of plastic.
Answer: Containers, buckets, bottles, chairs, baskets, etc.

Question 8. What is polythene?
Answer: Polythene is a polymer of ethene.

Question 9. What is the full form of PVC?
Answer: Polyvinyl Chloride

Question 10.Whether cotton cloth biodegradable or non-biodegradable?
Answer: Biodegradable

Question 11. Name the form of polyester which is replacing materials like glass and is used for making bottles and jars.
Answer: PET (Polyethylene Terephthalate)

Question 12. Name a synthetic fibre which is polyamide.
Answer: Nylon

Question 13. List any two properties of rayon.
Answer: The two properties of rayon are:

Rayon is a versatile fibre.

It can be dyed in different colours.

Question 14. Write some advantages of synthetic fibres.
Answer: Advantages of synthetic fibres are:

Synthetic fibres are strong and durable.

They do not shrink.

They are moth and insect-resistant.

Synthetic Fibres And Plastics Class 8 KSEEB Questions And Answers 

Question 15. List any three properties of plastics.
Answer: The three properties of plastics are:

They are non-corrosive in nature.

They are light in weight and durable.

They do not conduct heat.

Question 16. Pick the synthetic fibre out of the following?
(1)Cotton
(2)Nylon
(3)Jute
(4)Wool
Answer: (2)Nylon
Explanation: Cotton and Jute are from plant sources, Wool is from animal sources whereas Nylon is a synthetic fibre.

Question 17. Which of the following is a source of rayon?
(1)Wool
(2)PET
(3)Wood pulp
(4)Silk
Answer: (3)Wood pulp
Explanation: Rayon is obtained by chemical treatment of wood pulp.

Question 18. Polycot is obtained by mixing
(1)nylon and wool
(2)polyester and wool
(3)nylon and cotton
(4)polyester and cotton
Answer: (4) polyester and cotton

Question 19. Which is a thermosetting plastic?
(1)Melamine
(2)Polythene
(3)PVC
(4)Nylon
Answer: (1) Melamine
Explanation: Thermosetting plastics when moulded once can not be softened by heating. Examples are bakelite and melamine.

Question 20. The material similar to silk in appearance is
(1)Nylon
(2) Rayon
(3)Polyester
(4) Terylene
Answer: (2)Rayon
Explanation: Rayon is obtained by chemical treatment of wood pulp. Rayon is cheaper than silk and can be woven like silk.

Question 21. The most suitable material for the preparation of handles of cooking utensils is
(1) Polythene
(2)PVC
(3) Nylon
(4) Bakelite
Answer: (4) Bakelite
Explanation: Bakelite is a bad conductor of heat and it does not get soft on heating hence Bakelite is used to prepare handles of cooking utensils.

Question 22. Which of the following is not a common property of plastics?
(1)Non-reactive
(2)Light in weight
(3)Durable
(4)Good conductor of electricity
Answer: (4) Good conductor of electricity
Explanation: Plastic is a bad conductor of electricity.

Question 23. Which of the following represents the correct match for items in Column A with those in Column B?
ColumnA                   Column B
Nylon                        1) Thermoplastic
PVC                           2)Thermosetting plastic
Bakelite                     3) Fibre
Answer:
Nylon-2)
PVC-1)
Bakelite-3)

Question 24. Which of the following groups contain all synthetic substances?
(1)Nylon, Terylene, Wool
(2)Cotton, Polycot, Rayon
(3)PVC, Polythene, Bakelite
(4)Acrylic, Silk, Wool
Answer: (3) PVC, Polythene, Bakelite
Explanation:

• In options a) and c) there is wool which is extracted from an animal source.
• In option b) there is cotton which is from a plant source.
• Hence the answer is (c) PVC, Polythene, Bakelite.

Question 25. The material which is commonly used for making kitchen containers is
(1) P V C
(2) Acrylic
(3) Teflon
(4) PET
Answer: (4) PET
Explanation: PET or Polyethylene tetrathionate is lightweight and is used in making kitchen containers.

Question 26. A synthetic fibre which looks like silk is obtained by chemical treatment of wood pulp. It is, therefore, known as artificial silk. What is its common name?
Answer: Rayon is known as artificial silk.

Question 27. Plastic articles are available in all possible shapes and sizes. Can you tell me why?
Answer: It is very easy to make moulds from plastic hence it is available in all possible shapes and sizes.

Question 28. Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?
Answer: Plastic is not bio-degradable and disposing of plastic waste is a major issue. Hence it is advised to avoid the use of plastic as far as possible.

Question 29. Why is it not advisable to burn plastic and synthetic fabrics?
Answer: Burning of plastic releases toxic gases which pollute the air. Hence it is not advisable to burn plastic and synthetic fabrics.

Question 30. Select the articles from the following list which are biodegradable.
(1) Paper
(2) Woollen clothes
(3) Wood
(4) Aluminium can
(5)Plastic bag
(6) Peels of vegetables
Answer: 3
1. Paper
2. Woollen clothes
3. Wood
4. Peels of vegetables

Free KSEEB Notes For Class 8 Science Synthetic Fibres And Plastics 

Question 31. A bucket made of plastic does not rust like a bucket made of iron. Why?
Answer: Plastic is a non-reactive material. To form rust it should react with water and oxygen. Hence plastic does not form rust.

Question 32. Rohit took with him some nylon ropes when he was going rock climbing. Can you tell why he selected nylon ropes instead of ropes made of cotton or jute?
Answer: Nylon ropes are strong, flexible and elastic when compared to jute and cotton ropes. Acrylic blankets are cheap, light in weight, more durable and available in a variety of colours and designs. They can be easily washed at home.

Question 33. A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?
Answer: Lady prefers acrylic blankets over wool blankets because acrylic blankets are cheap, light in weight, more durable and available in a variety of colours and designs. They can be easily washed at home.

Explanation Of Synthetic Fibres And Plastics In KSEEB Science 

Question 34.PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?
Answer: On heating, Thermoplastics get deformed and they can be easily bent. Whereas Thermosetting plastics cannot be softened by heating.

Question 35. Fill in the blanks.
(1)A polymer is a chain of many small units joined together which are called_______.
(2) synthetic fibres are also known as _____ fibres.
(3)The first fully synthetic fibre was________.
(4)A fibre similar to wool is________.
(5)A plastic used for making crockery is
Answer:
(1) monomers
(2) man-made fibres
(3) Nylon
(4) acrylic
(5)melamine

Question 36.Match items in List A with the items of List B.
List A.
Nylon
PET
Rayon
Thermosetting plastics
Teflon
List B.
(1)non-stick coating
(2)electric switches
(3)parachutes
(4) polyester
(5) artificial silk
Answer:
List A – List B
Nylon – (3) parachutes
PET – (4) polyester
Rayon – (5)artificial silk
Thermosetting plastics – (2) electric switches
Teflon – (1) non-stick coating

Question 37. Unscramble the jumbled words given below, related to synthetic materials.
(1) Story
(2) Lopmery
(3) Relyteen
(4) Respect
(5) Yespolter
(6) Felton
Answer:
(1) Rayon
(2) Polymer
(3) Terylene
(4) Plastic
(5) polyester
(6) Teflon

Question 38. Indicate whether the following statements are True or False. Also, write false statements in their correct form.
(1)The fabric terry wool is obtained by mixing terylene and wool.
(2)Synthetic fibres do not melt on heating.
(3)It is risky to wear synthetic clothes while working in the kitchen.
(4)Most plastics are biodegradable.
Answer:
1) True
2)False- Synthetic fibres melt on heating.
3)True because synthetic clothes melt on exposure to heat
4)False- Plastics are non-biodegradable

Question 39. Write about the importance of synthetic polymers in our life.
Answer: Following are the points to justify the importance of synthetic polymers in our life.
1. Nylon It is used for making ropes for rock climbing, fishing nets, raincoats, parachutes and tyre cords, etc.
2. Acrylic It is used for sweaters, tracksuits, linings for boots and gloves and In furnishing fabrics and carpets.
3. Terylene It is used in the textile industry to make clothes like sarees, tapestry and dress material. It is also mixed with natural fibre like cotton and wool to make more variety of clothes.
4. Plastics It is used to store food items, water, milk, pickles, dry food, etc. Plastic containers seem the most convenient. This is because of its lightweight, low price, good strength and easy handling as compared to metals. Plastics are used in cars, air crafts and spacecraft.

Question 40. Despite being very useful it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?
Answer: Plastic is a non-biodegradable material which poses a serious threat to nature. Disposing of plastic waste is the biggest problem we face to regret the use of plastics. Plastics cause soil pollution and air pollution by burning.
The usage of plastic should be reduced and used plastic should be recycled and reused to reduce its consumption.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions for Class 8 Science Chapter 1 Crop Production And Management Points To Remember

Crop: When plants of the same kind are grown and cultivated in one place on a large scale, it is called a crop. In India, crops can be broadly categorised into two types based on seasons- Rabi and Kharif crops.

Basic practices of crop production:

1)Preparation of Soil: One of the most important tasks in agriculture is to turn the soil and loosen it. The process of loosening and turning of the soil is called tilling or ploughing.
2)Sowing: Sowing seeds at appropriate depths and distances gives a good yield. A good variety of seeds is sown after the selection of healthy seeds. Sowing is done by seed drills.
3)Adding Manure and Fertilisers 
Fertiliser: Chemical substances that are rich in nutrients and essential for plant growth. The inorganic compounds contain nutrients such as nitrogen, potassium and phosphorus. They are made in factories. Examples: Urea, ammonium sulphate, potash, etc.
Manure: A natural substance prepared from the decomposition of plant and animal wastes (cow dung, animal bones, dead leaves, dead insects and vegetable wastes) by the action of microbes.
4)Irrigation: The supply of water to crops at appropriate intervals is called irrigation.
Method of Irrigation: Tradition methods of Irrigation: Moat, Chain pump, Dhekli, Rahat.
Modern methods of Irrigation: Sprinkler system, Drip system.
5)Protection from Weeds: Weeding involves the removal of unwanted and uncultivated plants called weeds.
6)Harvesting: Harvesting is the cutting of the mature crop manually or by machines.
7)Storage: Proper storage of grains is necessary to protect them from pests and microorganisms. Large-scale of storage of grains is done in silos and granaries to protect them from pests like rats and insects. Farmers store grains in jute bags or metallic bins. Food is also obtained from animals for which animals are reared. This is called animal husbandry.
Agriculture: The practice of growing plants and rearing animals on a large scale for food, fibre and other useful products.

Class 8 Science KSEEB Crop Production Notes 

Crop Production And Management Ncert Textbook Exercises

Question 1. Select the correct word from the following list and fill in the blanks.

float, water, crop, nutrients, preparation

1)The same kind of plants grown and cultivated on a large scale at a place is called______
2)The first step before growing crops is_______of the soil.
3)Damaged seeds would _______on top of the water.
4)For growing a crop, sufficient sunlight_____ and_____ from the soil are essential.

Answer: crop, preparation, floats, water, nutrients

Question 2.Match items in column A with those in column B.
A
1)Kharif crops
2)Rabi crops
3)Chemical fertilisers
4)Organic manure
B
(a) Food for cattle
(b) Urea and phosphate
(c) Animal excrement, cow dung, urine and plant waste.
(d) Wheat, gram, pea
(e) Paddy and Maize
Answer: 1)-(e) 2)-(d) 3)-(b) 4)-(c)

Question 3. Give two examples of each
1) Kharif crop
2) Rabi crop
Answer:1) Kharif crop: Paddy and Maize

2) Rabi crop: Wheat and gram

Question 4. Write a paragraph in your own words on each of the following:
Answer:
(1) Preparation of soil: Soil preparation is necessary before growing a crop. It involves tilling and loosening the soil. This allows the roots to penetrate deep in the soil and to breathe easily even when they are deep.
(2) Sowing: The process of putting seeds into the soil is called sowing. The tool used traditionally for sowing seeds is funnel-shaped. Nowadays, a seed drill is used for sowing with the help of tractors. This tool sows the seed uniformly at a proper distance and depth.
(3) Weeding: Some undesirable plants grow along with crops and these unwanted plants are weeds. The process of removing these unwanted plants is called weeding.
(4) Threshing: The process of separating the grain seeds from the chaff is called threshing.

Question 5. Explain how fertilisers are different from manure.
Answer:
Fertilisers:

• A fertiliser is an inorganic salt
• A fertiliser is prepared in factories
  
• A fertiliser does not provide any humus to the soil.
• Fertilisers are very rich in plant nutrients like nitrogen, phosphorus and potassium

Manures:

• Manure is a natural substance obtained from dung, human waste and plant residues.
• Manure can be prepared in the fields.
• Manure provides a lot of humus to the soil.
• Manure is relatively less rich in plant nutrients.

Question 6. What is irrigation? Describe two methods of irrigation which conserve water.
Answer: The artificial method of watering plants for assisting in their growth is called irrigation.
Two methods which help us to conserve water are:
1) Sprinkler irrigation system: This system has an arrangement of vertical pipes with rotating nozzles on the top. It is more useful in uneven and sandy land where sufficient water is not available.
2) Drip irrigation system: This system has an arrangement of pipes or tubes with very small holes in them to water plants drop by drop just at the base of the root. It is very efficient as water is not wasted at all.

Question 7. If wheat is sown in the Kharif season, what would happen? Discuss.
Answer: Wheat crop is sown from November/Decem- ber to March/April. It is grown in winter and requires less water. If wheat is sown in the Kharif season, its production will be decreased considerably.

Question 8. Explain how soil gets affected by the continuous plantation of crops in a field.
Answer: Continuous plantation of crops makes the soil poorer in certain nutrients from the soil. The soil becomes infertile. It does not get enough time to replenish the nutrients.

Question 9. What are the weeds? How can we control them?
Answer: The undesirable and unwanted plants which grow naturally along with the crop are called weeds. The growth of weeds can be controlled by adopting many ways. Tilling before sowing crops helps in the uprooting and killing of weeds, which may then dry up and get mixed with the soil. Weeds are also controlled by using certain chemicals called weedicides. Weedicides are sprayed in the fields to kill the weeds.

KSEEB Class 8 Science Solutions For Crop Production And Management 

Question 10. Arrange the following boxes in the proper order to make a flow chart of sugarcane production.
Sending crops to sugar factory – 1
Irrigation-2
Harvesting – 3
Sowing-4
Preparation of soil-5
Ploughing the field – 6
Manuring-7
Answer:
Preparation of soil – 1
Ploughing the field-2
Sowing-3
Manuring – 4
Irrigation – 5
Harvesting – 6
Sending crops to sugar factory – 7

Question 11. Complete the following word puzzle with the help of the clues given below.
Answer:
Down
1. Providing water to the crops.
2. Keeping crop grains for a long time under proper conditions.
3. Certain plants of the same kind grow on a large scale.
Across
1. A machine used for cutting the matured crop.
2. A rabi crop is also one of the pulses.
3. A process of separating the grain from the chaff.

Crop Production And Management Activities

Question 1. Take a beaker and fill half of it with water. Put a handful of wheat seeds and stir well. Wait for some time.
Answer: We observe that most of the seeds sink while some float on water. Damaged seeds become hollow and lighter so they float. In this way, we can separate damaged seeds from healthier ones.

Question 2. Jake moong or gram seeds and germinate them. Select three equal-sized seedlings out of these. Now take three empty glasses or similar vessels. Mark them A, B and C. To glass, A add little amount of soil mixed with a little cow dung manure. In the glass, B put the same amount of soil mixed with a little urea. Take the same amount of soil in glass C without adding anything  Now pour the same amount of water into each glass and plant the seedlings in them. Keep them in a safe place and water them daily. After 7 to 10 days observe their growth 

Answer: After 7-10 days we observed that the growth was fastest in glass B followed by glass A. Glass C showed mini-mum growth.

Question 3. Make the following Table in your notebook and complete it.
S.no     Food       Sources
1.         Milk
2.         Meat
3.         Egg
4.         Honey
Answer:

Crop Production And Management Additional Questions

Question 1. What is the basis for the classification of crops in our country?
Answer: In our country, crops are classified on the basis of the season in which they grow.

Question 2. Name the tool used for tilling the soil
Answer: Aplough

Question 3. Why should loose soil be levelled?
Answer: Loose soil should be levelled for sowing and irrigation.

Question 4. How is ploughing done these days?
Answer: Nowadays, ploughing is done by a tractor have- ing a multi pronged plough

Question 5. Why should grains be dried before storage?
Answer: Grains should be dried before storage to remove the excess moisture in them so that microbes are not able to attack the grains.

Crop Production And Management Class 8 KSEEB Questions And Answers 

Question 6. Name the methods applied for weeding.
Answer:

• Manual method
• Chemical method
• Biological method

Question 7. What are the advantages of manure?
Answer: Following are some advantages of manure:

• It enhances the water-holding capacity of the soil.
• It improves soil quality.
• It promotes the growth of soil-friendly microbes.
• It is renewable, biodegradable and eco-friendly.

Question 8. What are weedicides? Give some examples.
Answer: Weedicides are chemicals that are used to remove weeds. Some commonly used weedicides are 2, 4-D and metaphor.

Question 9. What is ploughing or tilling? State its advantages.
Answer: The process of loosening and turning the soil is called tilling or ploughing. This is done by using a plough. Ploughs are made of wood or iron.
The following are the advantages of ploughing or tilling:

• Ploughing loosens the soil and makes it aerated.
• It helps in mixing organic matter with the soil uniformly.
• It initiates the growth of natural agents and microorganisms and thus, keeps the soil fertile.
• It increases the water-holding capacity of the soil.
• It helps in the easy penetration of roots into the soil.

Question 10. Write a short note on the terms:
1) Storage
2) Harvesting
Answer:
1)Storage: Storage of produce is an important task. If the crop grains are to be kept for a longer time, they should be safe from moisture, insects, rats and microorganisms. Before storing, the grains are properly dried in the sun to reduce their moisture in them. This prevents attack by insect pests, bacteria and fungi. Grains are stored by farmers in jute bags or metallic bins. However, large-scale storage of grains is done in silos and granaries to protect them from pests like rats and insects.
2)Harvesting: After the maturation of the crop, harvesting is an important task. In harvesting, crops are pulled out or cut close to the ground. It usually takes 3 to 4 months for a cereal crop to mature. Harvesting in our country is either done manually by sickle or by a machine called a harvester.  sowing seed also depends upon the seed size.

Question 11. Why the depth at which seeds are planted is important?
Answer: If the seed is planted too deep then it will not get enough sunlight to germinate. If the seed is planted too shallow then it will not get enough soil to support germination. The depth for sowing seeds also depends upon the seed size.

Question 12. Why is it advisable to wash fruits and vegetables before using them?
Answer: Because fruits and vegetables may contain many pesticides, used during crop production practices, on them along with other germs and dust.

Question 13. What is a plough?
Answer: A plough is equipment for ploughing. It is mainly made of a wooden shaft called a plough-shaft, attached to a triangular iron blade called a ploughshare.

Question 14. Name any two fertilisers.
Answer: NPK, Diammonium phosphate

Question 15. What is the process of separation of grain from chaff called?
Answer: Winnowing

Crop Production And Management Multiple Choice Questions

Question 16. Which one of the following conditions is not essential to grow maize?
1) High temperature
2) Humidity
3) Low temperature
4) Rainfall
Answer: 3) Low temperature
Explanation: Maize is grown in a warm and tropical climate. The optimum temperature for growing maize is between 18°c -27 °c during the day and 14-15°c at night. Hence a cold climate is not essential to grow maize.

Question 17. Propagation of ginger is generally done using
1) Seed
2) Stem (rhizome)
3)Root
4) Leaf
Answer: 2) Stem (rhizome)

Question 18. Which of the following statement is not true for organic manure?
1) It enhances the water-holding capacity of the soil.
2) It has a balance of all plant nutrients.
3) It provides humus to the soil.
4) It improves the texture of the soil.
Answer: 2) It has a balance of all plant nutrients.
Explanation: Organic manure is obtained by the decomposition of plants and animal waste which makes the soil nutrient-rich. But it does not mean that organic manure provides all the nutrients in the required amount hence option 2) is wrong.

Question 19. The term used for the process of separation of grains from the chaff is
1) Sieving
2) Threshing
3) Winnowing
4) handpicking
Answer: 3) Winnowing
Explanation: Winnowing is a process used to separate grains from the chaff by removing the scaly inedible chaff surrounding the grain. A machine called Combine is used for this process. The combine is a mixture of a harvester and a thresher.

Explanation Of Crop Production And Management In KSEEB Science 

Question 20. Read the statements given below.
1) Seeds require moisture for germination.
2) Plants can absorb nutrients mostly in dissolved form.
3) Irrigation protects crops from both frost and hot air currents.
4) Irrigation improves soil texture. Choose the combination of statements which indicate the need to irrigate crops.
1) 1 and 2
2) 1, 2, 3
3) 1, 2, 3, 4
4) 1, 3
Answer: 1) 1 and 2
Explanation: Irrigation supplies water to the crops when required and this will help the seed germinate by providing moisture to the seed. Plants readily absorb nutrients along with water in a dissolved form.

Question 21. Which of the following tools would a farmer use to remove weeds from the field?
1) Hoe
2) Plough
3) Axe
4) Cultivator
Answer: 1) Hoe
Explanation: Hoe is used to remove weeds and to loosen the soil. He works like a blade. Axe is used to cut trees. Plough is used for tilling the soil. The cultivator is used for ploughing.

Question 22. Which of the following is not true for fertilisers?
1) They increase the yield.
2) Their excessive use disturbs the balance of nutrients in the soil.
3) They are generally used in small quantities.
4) They are environment-friendly.
Answer:4) They are environment-friendly.
Explanation: Fertilisers are chemical substance that is rich in particular nutrients. Fertilizers indeed help in yield increase. But the long-term and excess usage of fertilizers will reduce soil fertility and pollutes the water bodies. By seeing through the rain.

Question 23. Given below are statements about the harmful effects of weeds on crop plants.
1) They interfere with harvesting.
2) They help crop plants to grow healthily.
3) They compete with crop plants for water, nutrients, space and light.
4) They affect plant growth. Choose the correct combination of statements.
(1) 1, 3, 4 (3) 3, 4
(2) 3 only
(4) 1, 2, 3, 4
Answer: (1) 1, 3, 4
Explanation: Weeds are unwanted plants that grow along with the grown crops. They compete for nutrients, water and sunlight with crops thereby affecting the health of crops and the yield.

Question 24. The process of loosening and turning of soil is called
(1) Irrigation and manuring
(2) Digging and winnowing
(3) Tilling and ploughing
(4) Harvesting and storage
Answer: (3) Tilling and ploughing
Explanation: Tilling and ploughing are the first steps in preparing the land for cultivation. Ploughing is done by using a plough which is made of either wood or iron.

Question 26. The monsoon season in our country is during the months
1) April to December
2) June to September
3) November to March
4) January to May
Answer: 2) June to September

Question 27. The system of irrigation wherein water is supplied drop by drop near the roots of plants, is called
1) Pulley system
2) Drip system
3) Sprinkler system
4) Lever system
Answer: 2) drip system
Explanation: Pulley system is a traditional irrigation method where water is lifted from wells or other water sources and crops are watered. This is done by using the pulley chain and human labour or animals.
The perpendicular pipes, having rotating nozzles on top, are joined to the main pipeline at regular intervals. When water is allowed to flow through the main pipe under pressure with the help of a pump, it escapes from the rotating nozzles. It gets sprinkled on the crop as if it is raining
The Lever system is a traditional irrigation method where humans or animals are used to lift the water from its source. This is a less efficient irrigation method.

KSEEB Class 8 Science Chapter 1 Important Questions 

Question 28. Pick out the odd one from the following words given in the box and give the reason for it. Plough, Seed Drill, Hoe, Chain Pump, Sickle
Answer: The answer is Seed drill. The seed drill is modern equipment used to sow the seeds. Whereas Plough, Hoe, Chain pump and sickle are old and traditional equipment used in agriculture.

Question 29. If you are given a dry piece of land for cultivation what will you do before sowing the seeds?
Answer: Before sowing, seed land should be prepared for cultivation. Tilling and ploughing are the first steps in preparing the land for cultivation. Ploughing is done by using a plough which is made of either wood or iron.

Question 30. State whether the following statements are True or False. Correct the false statements.
1) Using good quality seed is the only criterion to get a high yield.
2) Growing different crops in different seasons in the same field will deplete the soil of nutrients.
3) All crop plants are sown as seeds in the field.
4) Cells of root nodules of leguminous plants fix nitrogen.
5) Freshly harvested grains must be dried before storing.
Answer:
1) False: To get good yield appropriate agricultural practice, nutrient water is very essential along with good quality seeds.
2) False: It enriches the soil
3) False: Some crops need transplantation Ex: Ginger
4) False: Bacteria called Rhizobium present in the root nodules of leguminous plants fix nitrogen

Question 31. During which months do farmers grow mustard in India?
Answer: From October to March farmers grow mustard in India.

Question 32. Which activity of the farmer can promote the growth of earthworms and microbes in the field?
Answer: Loosening the soil/maintaining high moisture levels in the soil.

Crop Production And Management Short-Type Answer Questions

Question 1. Beera wants to practice crop rotation in his field. Suggest a Rabi crop and a Kharif crop which will replenish his field with nitrogen. Which crop replenishes nitrogen and why?
Answer:
Kharif: Rice or Soyabean,
Rabi: Pea or Wheat.
Pea/Soyabean are legumes that will fix nitrogen with the help of Rhizobium.

Question 2. Match the agricultural implements given in Column A with their use given in Column B.
Column A                           Column B
Sickle                                  Ploughing
Hoe                                     Slowing
Seed Drill                           Harvesting
Sprinkler                            Irrigation
Answer:
Sickle                                   Harvesting
Hoe                                     Ploughing
Seed Drill                            Slowing
Sprinkler                             Irrigation

Question 3. What are organic foods?
Answer: Food crops grown without using any chemicals including fertilizers, weedicides and pesticides are known as organic food.

Question 4. From the word puzzle, Find at least eight words which are farmer’s friends. Classify them into living and non-living.

Answer:

• Living: Seed, Earthworm, Rhizobium, Microbes, Ox
• Non-Living: Plough, Urea, NPK, Mature, Hoe.

Question 5. (1)Name the tool used with a tractor for sowing seeds in a field.
                     (2) What are the advantages of using this tool?
Answer:
1) The seed drill is the tool used with a tractor for sowing seeds in a field.
2) Advantages of seed drill are as follows

• It saves time and labour.
• After sowing seeds are covered by soil which will protect seeds from.
• Seeds are sown at uniform distances and depths. This avoids overcrowding of the seeds in one location.

Simplified Notes For KSEEB Class 8 Science Crop Production 

Question 6. (1) Name the practice followed for large-scale rearing of farm animals.
(2) What facilities are provided to farm animals?
Answer:
(1) Animal Husbandry
(2) Animals should be provided with shelter, food and care.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Class 8 Science Chapter 5 Coal And Petroleum Points To Remember

Natural Resources: Resources available in nature for the welfare of mankind.

Types of Natural resources:

Inexhaustible: Resources present in unlimited nature and will not be exhausted even if used continuously. Example: Sunlight, air.

Exhaustible: Resources which are limited and can soon get exhausted because of excessive use Example: Coal, petroleum, natural gas

Fossil fuels:  Fuels formed by the natural bacterial decomposition of buried dead plants and animals under extreme temperature and pressure.

Carbonisation: The slow process of conversion of dead vegetation into coal.

Destructive distillation: The process of heating a complex substance in a limited supply of air so that it breaks down to form simpler substances.

Coke, coal tar and coal gas are the main products of the destructive distillation of coal.

Peat, lignite, bituminous and anthracite are the four types of coal.

Petroleum is also called crude oil or black gold.

Fractional Distillation: The process of refining petroleum in refineries based on their boiling points.

Petroleum gas, petrol, naphtha, kerosene, diesel, fuel oil, lubricating oil and bitumen are products obtained from fractional distillation petroleum.

Natural gas is found under the crust of the earth above the layers of petroleum.

Natural gas mainly consists of methane.

Excessive burning of fossil fuels releases carbon dioxide which traps solar radiation in the atmosphere and causes the greenhouse effect and leads to global warming.

Petrochemicals: Chemicals derived from petroleum or natural gas.

We should use fossil fuels judiciously.

KSEEB Solutions Class 8 Coal And Petroleum Questions 

Coal And Petroleum Ncert Textbook Exercises

Question 1. What are the advantages of using CNG and LPG as fuels?
Answer:
The advantages of using CNG and LPG as fuels are :

1. They can be burnt directly
2. They can be transported easily through pipelines
3. They are clean fuels and do not give smoke when burnt
4. They give a lot of heat energy when burnt

Question 2. Name the petroleum product used for surfacing roads.
Answer: Bitumen

Question 3. Describe how coal is formed from dead vegetation. What is this process called?
Answer: Millions of years ago, dense forests got buried under the soil due to natural processes like storms, floods and earthquakes. These got compressed as more and more soil got deposited over them. When they got buried deep in the soil, they were exposed to very high pressure and temperature. Under these conditions, they slowly got converted into coal. This process of the formation of coal from dead vegetation is called carbonisation.

Question 4. Fill in the blanks :
1) Fossil fuels are_____ and _______
2) Process of separation of different constituents from petroleum is called  ______
3) Least polluting fuel for vehicles is _______
Answer:
1) Coal, petroleum and natural gas
2) refining
3) compressed natural gas

Question 5. Tick True/False against the following statements.
1) Fossil fuels can be made in the laboratory (T/F)
2) CNG is a less polluting fuel than petrol and diesel (T/F)
3) Coke is an almost pure form of carbon (T/F)
4) Coal tar is a mixture of various substances (T/F)
5) Kerosene is not a fossil fuel (T/F)
Answer:
(1) False
(2) True
(3) False
(4) True
(5) False

Question 6. Explain why fossil fuels are exhaustible natural resources.
Answer: Fossil fuels take millions of years to be formed. They are limited in nature and cannot be replenished easily once consumed. Hence, they are considered as exhaustible natural resources.

Question 7. Describe the characteristics and uses of coke.
Answer:
Characteristics of coke

1. Tough
2. Porous
3. Black in colour
4. Produce a very little smoke
5. Uses of coke
6. Manufacture of steel Year
7. Good reducing agent
8. As fuel and producing water gas

Question 8. Explain the process of formation of petroleum.
Answer: Petroleum was formed from dead organisms that got buried in the sea millions of years ago. These dead bodies got covered with layers of sand and Natural clay. Lack of air, high temperature and high pressure transformed these dead organisms into petroleum and natural gas.

Question 9. The following table shows the total power shortage in India from 1991 – 1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y- axis and the year on the X-axis.

Answer:

Class 8 Science Chapter 5 Coal And Petroleum KSEEB Answers 

Coal And Petroleum Activities

Question 1. Make a list of various materials used by us in daily life and classify them as natural and man-made
Answer:
Natural

1. Air
2. Sunlight
3. Water
4. Minerals
5. Forests

Man-made

1. Clothes
2. Plastics
3. Fan
4. Cement
5. Cosmetics
   

Coal And Petroleum Additional Questions

Question 1. What does CNG stand for?
Answer: Compressed Natural gas.

Question 2. Name the petroleum product used as fuel for stores, lamps and jet aircraft.
Answer: Kerosene

Question 3. Expand PCRA
Answer: Petroleum Conservation Research Association.

Question 4. While driving what are the tips we must follow to save petrol/diesel / natural gas?
Answer:

1. Ensure correct tyre pressure
2. Ensure regular maintenance of the vehicle
3. Drive at a constant and moderate speed
4. Switch off the engine at traffic lights or at a place where you have to wait.

Question 5. We read in newspapers that the burning of fuels is a major cause of global warming. Explain why?
Answer: Fossil fuels are generally mixtures of carbon-based compounds. On burning fossil fuels such as coal, petroleum and natural gas, produce carbon dioxide gas which is a greenhouse gas. The increase in levels of carbon dioxide in the atmosphere causes global warming.

Question 6.
1) What will happen if all the coal and petroleum reserves are depleted?
2) What can be done by you to prevent the depletion of coal and petroleum?
Answer:

1. If all the coal and petroleum reserves are depleted, we will not have fuels for our vehicles, factories and houses as they take a very long time to replenish.
2. We can prevent the depletion of coal and petroleum by following the ways
3. Use alternative fuels.
4. Use public transport and bicycles for short distances.
5. Use carpools to go to work or to school.

Question 7. Name some renewable sources of energy.
Answer: Water, wind, solar.

Question 8. Give some examples of fossil fuels.
Answer: Coal, petroleum, natural gas.

Question 9. Name the elements present in coal.
Answer: Carbon, oxygen and sulphur.

Question 10. List four varieties of coal.
Answer: Peat, lignite, bituminous, anthracite.

Question 11. Write the full form of LPG.
Answer: Liquefied Petroleum Gas.

Question 12. What is the purest form of carbon?
Answer: Coke

Question 13. Name three constituents of petroleum and write their uses also.
Answer:
The three constituents of petroleum are:

1. Petrol
2. Paraffin wax
3. Diesel

Uses:

Petrol: It is used as a motor fuel and for dry cleaning.

Paraffin wax: It is used for making ointments, candles, vaseline, etc.

Diesel: It is used as a fuel for heavy motor vehicles and electric generators.

Question 14. Name two products that you obtain from the destructive distillation of coal. What is the residue left in this process? Give one main use of this residue.
Answer:

1. The two important products obtained from the destructive distillation of coal are Coal gas and coal tar.
2. The residue left in this process is coke. Coke is used mainly as a reducing agent in the extraction of metals.

Question 15. Define the term ‘petrochemicals’.
Answer: Petrochemicals are substances obtained from petroleum and natural gas. They are used in the manufacture of detergents, fibres, polythene, etc.

KSEEB Class 8 Chapter 5 Coal And Petroleum Multiple Choice Questions

Question 16. Various materials which are obtained from nature are called natural resources. Which of the following is not a natural resource?
1. Minerals
2. Water
3. Soil
4. Plastic
Answer: 4. plastic
Explanation: Minerals, water and soil are natural resources whereas plastic is a man-made substance.

Question 17. Air is a natural resource and cannot be exhausted by human activities. It is known as an inexhaustible natural resource. Which of the following is another inexhaustible natural resource?
1. Coal
2. Petroleum
3. Sun-light
4. Minerals
Answer: 3. Sun-light
Explanation: Coal, petroleum and minerals are non-renewable sources of energy, which can get exhausted whereas sunlight is a renewable resource.

Question 18. Which of the following is a pair of exhaustible natural resources?
1. Coal and soil
2. Air and sunlight
3. Water and petroleum
4. Wildlife and minerals
Answer: 4. Wildlife and minerals
Explanation: Coal and Soil, air and sunlight, water and petroleum. All these natural resources cannot be exhausted by human consumption and other uses. Wildlife and minerals are exhaustible natural resources, which are available in limited quantities and will be exhausted as a result of continuous use.

Question 19. Coal is processed in industries to get some useful products. Which of the following is not obtained from coal?
1. Coke
2. Coal tar
3. Coal gas
4. CNG
Answer: 4. CNG
Explanation:

1. CNG is compressed natural gas which is made by compressing the natural gas.
2. CNG is a petroleum product whereas coke, coal tar and coal gas are obtained from coal.

Question 20. Exhaustible natural resources are:
1. Unlimited in quantity.
2. Not dependent on nature.
3. Limited in quantity.
4. Not exhausted by human activities.
Answer: 3. Limited in quantity.
Explanation: Exhaustible natural resources are limited resources, which are available in limited quantities and are going to be exhausted by continuous human use. Wildlife, petroleum, water and minerals are examples of Exhaustible natural resources.

Question 21. Fossil fuels are obtained from:
1. Remains of non-living materials.
2. Dead remains of birds only.
3. Dead remains of insects only.
4. Dead remains of living organisms.
Answer: 4. Dead remains of living organisms
Explanation: Fossil fuels are obtained millions of years ago remains of dead remains of living organisms. Get buried under the earth.

Question 22. Coal is formed from the remains of
1. Vegetation only
2. Animals only
3. Both vegetation and animals
4. Neither vegetation nor animals
Answer: 1. Vegetation only
Explanation: Coal is a fossil fuel formed from the remains of prehistoric plants or animals. The formation of coal occurs over millions of years via a process known as carbonation.

Question 23. Which substance is formed by the carbonisation of dead vegetation?
1. Coal
2. Coke
3. Coal gas
4. Coal tar
Answer: 1. Coal
Explanation: The formation of coal occurs over millions of years via a process known as carbonation. In this process, dead vegetation is converted into carbon-rich coal under very high temperatures and pressure.

Question 24. Naphthalene balls are obtained from coal tar and are used as:
1. Mosquito repellant
2. Honey bee repellant
3. Moth repellant
4. Snake repellant
Answer: 3. Moth repellant
Explanation: Naphthalene balls are chemical pesticides and deodorants, the characteristic smell of naphthalene makes the insects and moths run away from naphthalene stored under clothes etc.

Question 25. Which of the following is not a constituent of petroleum
1. Paraffin wax
2. Lubricating oil
3. Petrol
4. Coke
Answer: 4. Coke
Explanation: Coke is not a constituent of petroleum. It is almost a pure form of carbon.

Question 26. Petroleum was formed from organisms:
1. Living on the land
2. Living on the plants
3. Living in the sea
4. Living on the rocks
Answer: 3. Living in the sea
Explanation: Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled down at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, the absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.

Question 27. Choose the incorrect statement from the following:
1. It is difficult to transport natural gas through pipes.
2. The disadvantage of natural gas is that it can not be used directly for burning in homes.
3. Natural gas is stored under high pressure as compressed natural gas.
4. Natural gas cannot be used for power generation.
Answer:  1. It is difficult to transport natural gas through pipes.
Explanation: Natural gas is a naturally occurring hydrocarbon gas, which is extracted from the petroleum deposits deep beneath the earth. It isa highly flammable gas, therefore, it is difficult to transport through pipes.

Question 27. You are provided with a mixture of petroleum and water. Can you suggest a method to separate the two?
Answer: Decantation is the method used to separate a mixture of petroleum and water.

Question 28. Name the petroleum product used as fuel for stoves, lamps and jet aircraft.
Answer: Kerosene is the petroleum product used as fuel for stoves, lamps and jet aircraft.

Question 29. Fill in the blanks in the following sentences.
1.Cialis one of the ________used to cook food.
2. When heated in air, coal burns and produces mainly _____ gas.
3. Coal tar is black and thick with an _______ smell.
4.Petroleum, _____ and _____ are fossil fuels.
5. Forests and coal are _____ natural resources.
Answer:
1. Fuel
2. Carbon-di-oxide-gas
3. Thick
4. Coal
5. Exhaustible

Question 30. The underlined words in the following sentences have been jumbled up. Write them in their correct form.
1. Loca is obtained from mines.
2. Umpetlore is a fossil fuel.
3. Rineryfe is a place where various fractions of petroleum are separated.
4. Keenrose is a fuel used in jet crafts.
5. Nutsgilh is an example of inexhaustible natural resources.
Answer:
1. Coal
2. Petroleum
3. Refinery
4. Kerosene
5. Sunlight

Coal And Petroleum Class 8 Science KSEEB Guide 

Question 31. Write True/False against the following statements.
1. Oxygen is an exhaustible natural resource.
2. Resources which are present in unlimited quantity in nature are called exhaustible natural resources.
3. Wildlife is an exhaustible natural resource.
4. Under high temperatures and pressure, dead plants get slowly converted to coal.
5. CNG is a less polluting fuel than petrol and diesel.
Answer:
1. False
Explanation: Oxygen is not an exhaustible natural resource.
2. False
Explanation: Resources which are present in unlimited quantity in nature are called inexhaustible natural resources.
3. True
4. True,
5. True.

Question 32. Sunlight and air are inexhaustible natural resources. Comment.
Answer: Sunlight and air are present in unlimited quantity in nature and are not likely to be exhausted by human activities or by any other means. Hence Sunlight and the air are inexhaustible natural resources.

Question 33. Some natural resources are given in a box. Classify them into the exhaustible and inexhaustible natural resources.
Air, Coal, Natural gas, Sunlight, Petroleum, Minerals, Forests and Oxygen.
Answer:
Exhaustible                        Inexhaustible
Coal                                   Air
Forests                              Oxygen
Minerals                           Sunlight
Petroleum                        Natural gas

Question 34. Write the characteristics and some important uses of coal.
Answer:
Characteristics of coal.

1. It is a fossil fuel.
2. It is Combustible.
3. It is as hard as stone and is black in colour.
4. When it is burned in the air it releases CO₂

Uses of Coal

1. Coal is one of the fuels used to cook food.
2. Coal is also used as fuel in various industries.
3. It is also used in thermal power plants to produce electricity.
4. Earlier, it was used in railway engines to produce steam to run the engine.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions Class 8 Science Chapter 6 Conservation Of Plants And Animals Points To Remember

Biodiversity:

Occurrence of an innumerable number of different types of organisms and the whole range of their varieties (biotypes) adapted to different climates, environments and areas.

Wildlife sanctuary, national park, and biosphere reserve are names given to the areas meant for the conservation and preservation of forests and wild animals.

Biodiversity refers to the variety of living organisms in a specific area.

Plants and animals of a particular area are known as the flora and fauna of that area.

Endemic species are found only in a particular area.

Endangered species are those which are facing the danger of extinction.

Red Data Book contains a record of endangered species.

Migration is the phenomenon of the movement of a species from its own habitat to some other habitat for a particular time period every year for a specific purpose like breeding.

We should save, reuse and recycle paper to save trees, energy, and water.

Reforestation is the restocking of destroyed forests by planting new trees.

Flora: Different types of plants belonging to an area. Example: Silver Ferns, Sal, Teak, Mango, etc.
Fauna: Animals found in an area- Example: Dog, Frog, Insects, Bull Jackal, etc.
Endemic Species: Species of plants and animals found exclusively in a particular area. These are not naturally found anywhere else.
Extinct Species: Species of plants and animals which have already been lost. Examples: Dodo, Indian Cheetah, Pink-headed Duck, etc.
Threatened Species: Species that are liable to become extinct if it is not allowed to realize their full biotic potential by removing the cause of the threat.
Type of Threatened Species:
1. Endangered Species: A species of animal or plant that is seriously at risk of extinction. Example: Indian rhinoceros, Asiatic ion, Asiatic wild ass, etc
2. Vulnerable Species: A vulnerable species is a species of animals or plants which are likely to become endangered unless something changes.
Example: Chinkara deer and Black buck, Golden Langur, etc
3. Rare Species: Species whose populations are originally scarce and scattered in the world.
4. National Parks: Protective areas reserved exclusively for the betterment of wildlife. These are established with the approval of the legislature.
Examples: Hazaribagh National Park in Jharkhand, Desert National Park in Rajasthan, etc
5. Sanctuaries: Hunting prohibited areas set up by the government are known as sanctuaries. These are only for the protection of wild animals. Example: Jaldapara in Madarihat, West Bengal), Keoladeo Ghana in Bharatpur (Rajasthan)
6. Migration: The regular, periodic, two-way movements of birds and some animals from their place of residence to some other place along well-defined routes. It is linked to seasonal factors, breeding, shortage of foods, etc. The Bharatpur Bird Sanctuary is known for its migratory birds.

Class 8 Science Conservation of Plants And Animals KSEEB Questions 

Conservation Of Plants And Animals Ncert Textbook Exercises

Question 1. Fill in the blanks :
1. A place where animals are protected in their natural habitats is called a wildlife sanctuary.
2. Species found only m a particular area is known as biodiversity.
3. Migratory birds fly to faraway places because of climate changes.

Question 2. Differentiate between the following.
1. Wildlife Sanctuary and Biosphere reserve
2. Zoo and Wildlife sanctuary
3. Endangered and Extinct Species
4. Flora and Fauna
Answer:
1. Wildlife Sanctuary

1. This is an area where wild animals are protected and preserved.
2. It is a place found in

Biosphere reserves

1.  It helps to maintain the biodiversity and culture of the area.
   
2. Abiosphere reserves may also d areas of other protected Wildlife Sanctuary

2. Zoo

1. It is a place where we protect animals.
   
2. Here artificial surroundings are made for
   
3. Here animals are supplied with prepared food.
   

Wildlife Sanctuary

1. Here, too, wild animals are protected and preserved.
   
2. They live in their natural habitat or environment.
   
3. They get their food from forests themselves.

3. Endangered Species

1. These are those species that are facing the danger of extinction.
   
2. Tiger is an example of an endangered species.

Extinct Species

1. They are the species that have already vanished from the earth.
2. Dinosaur is an example of extinct species.

4. Flora

1. Flora Flora is a plant found in a particular region.
   
2. Sal, mango, Jamun, etc. are examples of flora. Biosphere Reserves 121/105

Fauna

1. Fauna is the animals found in a particular region.
   
2. Chinkara, blue-bell, deer, cheetah, etc. are examples of fauna.

Question 3. Discuss the effects of deforestation on the | 5. following.
1. Wild animals
2. Environment
3. Villages (rural areas)
4. Cities
5. Earth
6. The next generation
Answer:
1. Wild animals: They won’t get their natural habitat and surroundings as well as food. They will migrate to another forest.
2. Environment: Climate changes disturb the environment. Global warming is caused due to accumulation of carbon dioxide.
3. Villages: Villagers cannot grow food because of no rain. So, drought situations will prevail. Villagers will move towns and cities.
4. Cities: Cities flooded with drought-affected villagers, will affect the environment. Food grains will either not be available or if available, they will be costlier.
5. Deforestation leads to changes in soil properties. The physical properties of the soil will get affected badly. The lands will be gradually converted into deserts.

Question 4. What will happen if
1. We co on cutting trees.
2. The habitat of an animal is disturbed
3. The top layer of soil is exposed
Answer:
1. If we go on cutting trees, then the following situation will arrive Climate change will affect the environment due to global warming and there will be no rain. The soil will become unfertile due to regular flooding of the topsoil.
2. If the habitat of an animal is disturbed, the animal may not be in a position of getting its natural habitat as well as food.
3. Removal of the top layer of soil by floods and heavy winds will expose the lower hard and rocky layers. This soil has less humus and less fertility.

Question 5.Answer in brief
1. Why should we conserve biodiversity?
2. Protected forests are also not completely safe for wild animals. Why?
3. Some tribes depend on the jungle. How?
4. What are the causes and consequences of deforestation?
5. What is Red Data Book?
6. What do you understand by the term migration?
Answer:
1. If biodiversity is not conserved, the life existing on earth, its interrelationships, and its relationship with the environment will be disturbed.
2. It is because despite all these the poachers keep killing or capturing the animals in these forests. That is why protected forests are also not completely safe for animals.
3. Some tribal life in the jungle. The jungle provides them with food and protection. That is why: they are fully dependent upon the forests.

Causes of deforestation:

1. Procuring land for cultivation.
2. Building houses and factories.
3. Natural Calamities like floods, drought,s and forest fires.
4. Consequence of deforestation
5. Global warming.
6. Soil erosion
7. Melting ice on poles.
8. Red Data Book is a book that keeps a record of all endangered animals and plants.
9. Migration is the phenomenon of movements of species from its own habitat to some other habitat for a particular time period every year for a change of climate and for the purpose of breeding.

KSEEB Science Class 8 Chapter 6 Guide 

Question 6. In order to meet the ever-increasing demand in factories and for shelter, trees are being continually cut Is it justified to cut trees for such projects?
Answer: Of course, to meet the ever-increasing demand in factories and for shelter, trees are being continually cut, which is not justified at all. fone tree is cut, a least five trees should be grown so that the reforestation process will remain continuous. But if trees are cut blindly and no trees are planted then the earth will face global warming, no rainfall, climate change, soil erosion, and deforestation. So, cutting trees for any reason at all is not justified.

Question 7. How can you contribute to the maintenance of the green wealth of your locality? Make a list of actions to be taken by you.
Answer: For the maintenance of the green wealth of my locality. I will prefer reforestation in the locality. I shall start a campaign, along with my friends, to make the people of the locality aware of the importance of trees. Once people become conscious of the importance of plants they will be requested to do the following-
Each family should plant at least one tree in the monsoon month.
During summer, they should assure the watering of the plants every day.
On the occasion of birthdays, marriage ceremonies, and other happy occasions, they should gift their friends and relatives.

Question 8. Explain how deforestation leads to reduced rainfall
Answer: Deforestation leads to the accumulation of CO, in the atmosphere which results in global warming as CO, traps the heat of the sun’s rays. The increase in the temperature of the earth will disturb the water cycle and reduce rainfall causing drought in the region.

Question 9. Find out about national parks in your state. Identify and show their location on the outline map of India.
Answer: There is not any national park in my native state but near national parks around my locality are Ranthambore, Bharatpur, and Sarika of
the nearby state of Rajasthan.

Question 10. Why should the paper be saved? Prepare a list of ways by which you can save paper.
Answer: The manufacturing of paper needs trees. By cutting trees, deforestation is caused. If the paper is saved or recycled, so many trees can be saved. To make one ton of paper17 full-grown trees are to be cut. Therefore, to stop deforestation, we should save paper. It can be saved by recycling. Paper can be recycled 5-7 times and can be used. If everyone who uses paper could save at least one sheet of paper in a day, we can save many trees in a year.

Question 11. Complete the word puzzle.
Down
1. Species on the verge of extinction.
2. A book carrying information about endangered species.
5. Consequence of deforestation.
Across
1. Species that have vanished.
3. Species found only in a particular habitat.
4. Variety of plants, animals, and microorganisms found in an area.

Conservation Of Plants And Animals Activities

Question 1. Add more causes of deforestation to your list and classify them into natural and man-made.
Answer:
Natural causes of deforestation:
1. Forest fires
2. Severe drought
Man-made causes of deforestation:
1. Wood for the manufacturing of paper.
2. Wood for fuel and the making of houses.

Question 2. Animal life is also affected by deforestation. How? List the points and discuss them in your class.
Answer:

1. Due to deforestation, a great disturbance is caused in the food chain.
2. Deforestation makes the animals homeless.
3. Due to deforestation, animals become easy prey for hunters.
4. Herbivorous animals face the scarcity of food due to deforestation.
5. Animals face the bad effects of natural calamities.

Question 3. List the factors disturbing the biodiversity of your area. Some of these factors and human activities may disturb biodiversity unknowingly. List these human activities. How can these be checked? Discuss in your class and write a brief report in your notebook.
Answer: Cutting of trees, rising air, water, and land pollution, excessive construction, and using more resources or their products affect the biodiversity harshly.

Important Questions On Conservation Of Plants And Animals Class 8 KSEEB 

Question 4. Try to identify the flora and fauna of your area and list them.
Answer:
Flora (trees and plants): Pipal, sal, teak, Kadam, babool, mango, guava, ferns, Arjun, Kelkar, etc., are flora present in our locality.
Fauna (animals): Blue-bull, chinkara, cheetah, deer, leopard, wolf, wild dog, etc., are the fauna present in our locality.

Question 5. Find out the endemic plants and animals of the region where you live.
Answer:

1. Endemic plants: Mahua, wild mango, sal, Jamun, etc.
2. Endemic animals: Bison, Indian giant squirrel, etc.

Question 6. Visit a nearby zoo. Observe the conditions provided to the animals. Were they suitable for animals? Can animals live in an artificial setting instead of their natural habitat? In your opinion, will the animals be comfortable in a zoo or in their natural habitat?
Answer:

1. A zoo tends to provide suitable conditions for the animals to live in, similar to their natural habitat.
2. Yes, animals can live in an artificial setting instead of their natural habitat, as they live in the natural environment and stay protected from people.
3. In my opinion, animals are safer in the zoo in comparison with their natural environment, because special care is taken for the animals in the zoo. But I think animals feel more comfortable living in their natural habitat as no one wants to live in prison.

Conservation Of Plants And Animals Additional Questions

Question 1. What is sanctuary?
Answer: An area where animals are protected from any disturbance to them and their habitat is called a sanctuary.

Question 2. Write the names of some parks and sanctuaries.
Answer: Dudhwa National Park, Bharatpur Bird Sanctuary, Kaziranga National Park, Nelapattu Bird Sanctuary, etc.

Question 3. Give examples of flora.
Answer: Teak, sal, mango, Jamun, Arjun, etc.

Question 4. Give examples of fauna.
Answer: Elephant, tiger, wild bear, etc.

Question 5. Name two endemic fauna.
Answer: Giant squirrel, bison.

Question 6. Name the first Reserve Forest of India.
Answer: Satpura National Park.

Question 7. What is the name of the reserved land used to protect biodiversity?
Answer: Biosphere Reserve.

Question 8. List the names of some migratory birds.
Answer: Siberian crane

1. Bar-headed goose
2. Arctic tern
3. Surkhab

Question 9. Write the names of some extinct animals.
Answer: Dodo, dinosaurs, mammoth, etc.

Question 10. What do you mean by deforestation?
Answer: The cutting of trees on a large scale is called deforestation.

Question 11. Mention the causes of deforestation.
Answer: The cause of deforestation could be:

1. Forest fires
2. Building houses, factories
3. Severe droughts
4. Using wood for some purposes
5. Human encroachment and procuring land for cultivation

Question 12. How does deforestation lead to frequent floods and droughts?
Answer: Deforestation results in the decreased water-holding capacity of the soil. This reduces the infiltration of water into the ground which causes floods. On the other hand, deforestation leads to a higher level of carbon dioxide in the atmosphere which causes global warming. The scarcity of trees disturbs the water cycle and may reduce rainfall leading to droughts.

Question 13. How can we protect wildlife?
Answer: Wildlife plays a significant role in maintaining a balance in the environment. They can be protected by establishing secured and protected areas, which are restricted for human activities that are against the protection of wildlife. Cutting trees hunting, and poaching are strictly banned there. Many of these areas are national parks and wildlife sanctuaries.

Question 14. Why is the conservation of biodiversity important?
Answer: Because of the following reasons, the conservation of biodiversity is important:

1. It boosts tourism and thus, plays a significant role in enhancing the economy of the country.
2. It maintains the fertility of the soil.
3. It helps in maintaining the ecological balance on the earth.
4. Biodiversity is a rich source for the study of genetics and evolution.
5. It helps in maintaining the weather by regulating climatic changes, rainfall, etc.

Question 15. What are ‘rare species? Give examples.
Answer: Rare species are uncommon and scarce, that is to say, their population is very small. Major steps are to be taken for their conservation and protection so that they may not fall under the category of endangered or extinct species. Examples: wild buffalo, Bengal fox, gaur, marbled cat, etc.

Question 16. For centuries human activities such as hunting and encroachment have led to the degradation of forests and the extinction of many species of plants and animals. The government of India has taken many steps to conserve forests and wildlife. But this movement will not be a success without the involvement of all of us.
1. What products are obtained from forests and wildlife?
2. How can we help in conserving forests and wildlife?
3. Can you name some organisations that are working against the killing or poaching of animals?
4. What values of humans are shown here towards nature?
Answer:
1. From forests: Wood for fire, timber furniture, medicines, forage for livestock, gums, raisins, papers, etc. From wildlife: Horns, skin, leather, fur, ivory, meat, fin, etc.
2. By saying No’ to animal products we can at least reduce their hunting and poaching.

1. By not cutting the trees and planting more saplings we can help in restoring the natural habitat of wild animals.
2. By creating awareness among people about the importance of forests and wildlife.

3. World Wide Fund for Nature (WWF), International Fund for Animal Welfare (IFAW), World Society for the Protection of Animals (WSPA)), etc.
4. They are cruel, money-minded, selfish, reckless, etc.

KSEEB Class 8 Conservation of Plants And Animals Exercise Solutions Multiple Choice Questions

Question 17. Wild buffalo is an endangered species because
1. Its population is diminishing
2. It has become extinct
3. It is found exclusively in a particular area
4. Its poaching is strictly prohibited
Answer: 1. Its population is diminishing

Question 18. Which one of the following changes may occur due to desertification?
1. Increased chances of floods.
2. Conversion of fertile land into a desert.
3. The decrease in atmospheric temperature.
4. Increase in water holding capacity of Bihar. soil
Answer: 2. Conversion of fertile land into a desert
Explanation: Soil is carried away by the wind there are no trees as there will be no roots to hold onto the soil. Thus topsoil erodes which will turn the land into a desert.

Question 19. Which one of the following statements is true about a Biosphere Reserve?
1. It is a protected area where only endemic species live.
2. It is meant only for the conservation of
3. It is meant to conserve both, the biodiversity and the culture of that area.
4. There are no other protected areas within its limits.
Answer:3.It is meant to conserve both, the biodiversity and the culture of that area.
Explanation: The biosphere reserve is the protected part of the land covered with forests. It is meant for the conservation of wildlife, biodiversity, and the traditional lifestyle of tribals.

Question 20. The place meant for the conservation of biodiversity in their natural habitat are
1. Zoological garden
2. Botanical garden
3. Wildlife sanctuary
4. National park
Answer: 3. Wildlife sanctuary, 4.National park
Explanation: In botanical gardens and zoological parks species are protected outside their natural habitat and ex-situ conservation. On the other hand, Wildlife sanctuaries and National parks are in-situ conservation where the conservation of biodiversity occurs in their natural habitat.

Question 21. Which one of the following statements is true about endemic species?
1. They are found exclusively in a specific habitat.
2. Endemic species can never become endangered.
3. They are found only in zoos and botanical gardens.
4. They are not affected by the destruction of their habitat.
Answer: 1. They are found exclusively in a specific habitat.
Explanation: Endemic species are those which are found exclusively in specific habitats. Endemic species get extinct when their habitat is destroyed by human activities or by the introduction of new species are introduced to the habitat.

Question 22. Which of the following feature is correct for a wildlife sanctuary?
1. It is an artificially created protected area for animals.
2. It is a protected area for threatened and endangered wild animals.
3. It is meant for the conservation of only plant species.
4. Capturing and poaching of animals is strictly prohibited here.
Answer: 1. It is an artificially created protected area for animals.
Explanation: The wildlife sanctuary is an artificially created protected area for animals.

1. Hence option 3. is wrong. Wildlife sanctuaries are not specific for threatened and endangered wild animals.
2. Hence answer 2. is wrong. Capturing and poaching animals is strictly prohibited everywhere.
3. Hence option 4. is not appropriate.

Question 23. Which statement is incorrect about endangered species?
1. Their number has decreased drastically.
2. They might become extinct in the near future.
3. They pose a danger to other animals.
4. Their natural habitat needs to be protected
Answer: 3. They pose a danger to other animals.

Question 24. What do blackbuck, elephant, python, and golden cat together represent in a forest?
1. Fauna
2. Flora
3. Ecosystem
4. Species
Answer: 1. Fauna
Explanation: Fauna is the animal’s in a particular area. Flora is a plant species in a particular area. The ecosystem includes the physical environment along with plants and animals of a particular area. A species is a group of inbreeding populations.

Question 25. The Red Data Book keeps a record of all the
1. Endemic species.
2. Extinct species.
3. Endangered plants
4. Endangered animals.
Answer: 1. Endemic species,2. Extinct species.
Explanation: Red Data book keeps a record of endangered animals and endangered plants. Different books are maintained for different species including plants, animals, and other species.

Question 26. Migratory birds fly to faraway areas during a particular time of the year. Which of the following conditions present in their habitat
during that time are responsible for this behavior?
1. Unavailability of food.
2. Extreme weather conditions.
3. Overcrowding.
4. Lack of nesting areas.
Answer: 1. Unavailability of food, 2.Extreme weather conditions.
Explanation: The migration of birds is a process of moving to different habitats due to adverse climatic conditions. Because of extreme weather
conditions, birds fail to gather food and they cannot lay their eggs.

Question 27. In our country, large patches of forests are being cleared for the cultivation of crops. The environmental impact of such a practice will lead to
1. Soil erosion
2. Soil conservation
3. Soil pollution
4. Soil fertility
Answer: 1. soil erosion
Explanation: Due to the cutting of trees, there will no roots to hold the soil, and because of this topsoil erodes by the action of wind.

Question 28. Why is it important to conserve forests?
Answer: Forest should be conserved for balance in nature and to conserve the ecosystem.

Question 29. Mention any one action that you have undertaken to conserve trees.
Answer: Donating old books and spreading awareness about deforestation.

Question 30. State whether the following statements are True or False. Correct the false statements.
1. There can be a wildlife sanctuary within a biosphere reserve.
2. Plants of a particular area are collectively termed fauna.
3. Deforestation leads to an increase in the water-holding capacity of the soil.
4. Bison is an endemic fauna of the Pachmarhi Biosphere Reserve.
Answer:
1. True.
2. False- Plants of a particular area are collectively termed flora.
3. False- Deforestation leads to a decrease in the water-holding capacity of the soil.
4. True.

Question 31. Can a forest regenerate naturally in a short period of time?
Answer: It takes a long period of time to regenerate the forest naturally.

Question 32. Name the first Reserve Forest of India.
Answer: Satpura National Park.

Question 33. Why are wildlife sanctuaries important for the conservation of plants and animals?
Answer: Wildlife sanctuaries are important for the conservation of plants and animals because in these areas poaching or killing animals, and disturbing animals by any means of human activity are prohibited. Moreover, in wildlife sanctuaries animals can live in their natural environment. This promotes their breeding and population increase.

Question 34. Why are endemic organisms in greater danger of becoming extinct?
Answer: Endemic organisms are those which can live in a particular geographical location. Any disturbance to their natural habitat will affect the endemic animals adversely hence they are in great danger of becoming extinct.

Question 35. How are even small animals important in an ecosystem?
Answer: Every organism forms a part of the food chain and ecosystem. Hence every organism is important to balance the ecosystem.

Question 36. A new species X is introduced in a forest. How is it likely to affect the local species of that area?
Answer: Introduction of new species in a forest leads to competition for food and place. Hence it will affect the native species present in the forest.

Question 37. Does soil erosion affect the fertility of soil? How?
Answer: Soil erosion leads to the washing out of soil fertile layer of soil. This leads to the desertification of land due to a lack of fertile soil.

Question 38. What is the unique feature of the biodiversity found in the Panchmarhi Biosphere Reserve?
Answer: The biodiversity found in Panchmarhi Biosphere Reserve is similar to that found in the upper Himalayan peaks and lower Western Ghats.

Question 39. Mention the aim of the Forest (Conservation) Act.
Answer: Aim of the Forest (Conservation) Act are as follows
To conserve natural forests and the animals present in the forest.
To meet the basic needs of the people living in the forest.

Question 40. What is biodiversity?
Answer: Biodiversity refers to the variety of plants and animals present in a particular habitat.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions Class 8 Science Chapter 7 Force And Pressure Points To Remember

Force:

A push or a pull, that changes or tends to change the state of rest or of uniform motion of an object or changes its direction or shape.

A force arises due to the interaction between two objects.

Force has magnitude as well as direction. The SI unit of force is Newton.

A change in the speed of an object or the direction of its motion or both implies a change in its state of motion.

Force acting on an object may cause a change in its state of motion or a change in its shape.

A force can act on an object with or without being in contact with it.

Types of Forces:

Contact Forces: The forces act on a body when the source of force is in actual contact with the body. The point where the force is applied on an object is called the point of application of force
1. Muscular Force: The force exerted by the muscles of the body. We make use of the muscular force of animals like bullocks, horses, and camels to get our activities done.
2. Mechanical Force: The force produced by a machine.
3. Frictional Force: The force that opposes the motion of an object.

Non-Contact Forces: Forces that do not involve physical contact between two bodies on which they act.
1. Magnetic Force: A magnet exerts a noncontact force on objects made of iron, steel, cobalt, or nickel.
2. Electrostatic Force: The force which results due to the repulsion of similar charges or attraction of opposite charges.
3. Gravitational Forces: The force that exists between any two bodies by virtue of their mass.

Pressure:

Thrust acting per unit surface area is called pressure. Thrust s the force acting on an object perpendicular to its surface. In the SI system, pressure is measured in newton per square meter which is equal to (1) pascal (Pa).

Like solids, fluids (liquids and gases) also exert pressure. A solid exerts pressure only in the downward direction due to its weight, whereas liquids and gases exert pressure in all directions. Hence liquids and gases exert pressure on the walls of their container.

The thick blanket of air that covers the earth is termed the atmosphere. The pressure exerted by the atmosphere is called atmospheric pressure. The tremendous atmospheric pressure surrounding us is not felt by us because the fluid pressure inside our bodies counterbalances the atmospheric pressure around us.

Class 8 Science Force And Pressure KSEEB Notes 

Force And Pressure NCERT Textbook Exercises

Question 1. Give two examples of each of the situations in which you push or pull to change the state of motion of objects.
Answer:

If a rubber ball or marble is placed on a very smooth surface and given a small push, it starts moving with some speed.

If a child is placed on a hanging swing in the state of rest and the swing is pulled again and again by a rope, the swing will move to and fro with a speed.

Question 2. Give two examples of situations in which applied force causes a change in the shape of an object.
Answer:

If an inflated balloon is taken and pressed from two sides with a hand, its shape gets changed.

If a plate of steel is beaten up with a hammer the shape of the plate will get change.

Question 3. Fill in the blanks in the following statements.
1. To draw water from a well we have to pull at the rope.
2. A charged body attracts an uncharged body toward it.
3. To move a loaded trolley we have to pull it.
4. The north pole of a magnet repels the north pole of another magnet.

Question 4. An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target Based on this information fill up the gaps in the statements using the following terms.
Muscular, contact, non-contact, gravity, friction, shape, attraction
1. To stretch the bow, the archer applies a force that causes a change in its______
2. The force applied by the archer to stretch the bow is an example of _______force.
3. The type of force responsible for a change in the state of motion of the arrow is an example of a _____ force.
4. While the arrow moves towards its target, the forces acting on it are due _____to ______ and that due to air.
Answer:
1. Shape
2. Muscular
3. Contact
4. Gravity, friction.

Question 5. In the following statements identify the agent exerting the force and object on which its acts. State the effect of the force in each case.
1. Squeezing a piece of lemon between the fingers to extract its juice.
2. Take out paste from a toothpaste tube.
3. A load is suspended from a spring while its other end is on a hook fixed to a wall.
4. An athlete making a high jump to clear the bar at a certain height.
Answer:
Agents exerting force

1. Fingers
   
2. Fingers
   
3. A load
4. An athlete

The object on which force acts

1. Lemon
   
2. Toothpaste tube
   
3. Spring
   
4. On the legs

Effect of force

1. Lemon juice is extracted
   
2. Toothpaste come out
   
3. The spring expands
   
4. Cleans the height

Question 6. A blacksmith hammers a hot piece of iron while making tools. How does the force due to hammering affect the piece of iron?
Answer: The shape of the hot piece of iron changes. It flattens and becomes thinner than earlier. This is the effect of force due to hammering the piece of iron.

Question 7. An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?
Answer: This is an electrostatic force.

Question 8. Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on
the bucket does not bring a change in its state of motion.
Answer: The forces that act on the bucket are as follows:
1. The pressure of water contained in it, exerted on its wall and on the base of the bucket.
2. Force of gravity by the earth
3. The water is contained in a bucket and the pressure of force is exerted on the wall of the bucket, which is sufficient to take it as a force. As the bucket is held in my hand, so I overcome the force of gravity of the earth. That is why these forces do not bring a change in the state of motion.

Question 9. A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Answer: The two forces that are acting on the rocket immediately after leaving the launching pad are:

Force of gravity of the earth acting downward and

The frictional force produced by air particles.

Question 10. When we press the bulb of a dropper with its nozzle kept in water, the air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
1. Pressure of water.
2. Gravity of the earth.
3. Shape of a rubber bulb.
4. Atmospheric pressure.
Answer: 4. Atmospheric pressure.

KSEEB Class 8 Science Chapter 7 Force And Pressure Questions 

Force And Pressure Activities

Question 1. Gives some examples of familiar situations involving the motion of objects. You can add more such situations or replace those given here. Try to identify the activities involved in each case as a push and/or a pull and record your observations. One example has been given to help you. Identifying Actions as Push or Pull
Answer:

Question 2. Choose a heavy object like a table or a box, which you can move only by pushing hard. Try to push it all by yourself. Can you move it? Now ask one of your friends to help you in pushing it in the same direction Is it easier to move it now? Can you explain why? Now push the same object, but ask your friend to push it from the opposite side Does the object move? If it does, note the direction in which it moves. Can you guess which one of you is applying a larger force?
Answer:
1. The box moves with difficulty when we push alone but moves easily if helped by our friend. Thus, force applied to an object in the same direction adds to one another.
2. When the object is pushed from the opposite side, it does not move. Thus, if two forces act in the opposite direction on an object the net force acting on it is the difference between the two forces.

Question 3. Take a rubber ball and place it on a level surface such as a tabletop or a concrete floor. Now, gently push the ball along the level surface Does the ball begin to move? Push the ball again while it is still moving. Is there any change in its speed? Does it increase or decrease? Next, place your palm in front of the moving ball. Remove your palm as soon as the moving ball touches it. Does your palm apply force on the ball? What happens to the speed of the ball now? Does it increase or decrease? What would happen if you let your palm hold the moving ball?

Answer: When we push the ball along the level surface, the ball begins to move. When we push the ball again while it is still moving, increases its speed. When we place our palm in front of the moving ball, decreases its speed. Hence, the force can change the state of motion.

Question 4. Take a ball and place it on a level surface as you did Make the ball move by giving it a push. Now place the ruler from your geometry box in its path In doing so, you would apply a force on the moving ball. Does the ball continue to move in the same direction after it strikes the ruler? Repeat the activity and try to obstruct the moving ball by placing the ruler such that it makes different angles to its path. In each case note your observations about the direction of motion of the ball after it strikes the ruler.
Answer: The ball changes direction after it strikes the ruler. Thus, a force can change the direction of motion of a moving object.

• A ball is set in motion by pushing it along a level surface and
• The direction of motion of the ball after it strikes the ruler placed in its path

Question 5. Some situations have been given in Column in which objects are not free to move. Column 2 of the Table suggests the manner in which a force can be applied to each object while Column 3 shows the action. Try to observe the effect of the force in as many situations as possible. You can also add similar situations using available material from your environment. Note your observations in Columns 4 and 5.
Answer: From the above actions, we can conclude that force can change the shape of an object.

Question 6. Take a pair of bar magnets. Place the longer side of one of the magnets over three round-shaped pencils or wooden rollers as shown in Fig. 11.4. Now bring one end of the other magnet near the end of the magnet placed on the rollers. Make sure that the two magnets do not touch each other. Observe what happens. Next, bring the other end of the magnet near the same end of the magnet placed on the rollers Note what happens to the magnet placed on the rollers every time another magnet is brought near it.
Answer: When unlike poles of the magnet are brought near the other magnet, they attract each other and move in the direction of another magnet. When like poles of a magnet are brought near to the other magnet, they repel each other and move in the direction away from the other magnet. Thus, the force exerted by a magnet on another magnet is a type of non-contact force.

Question 7. Take a plastic straw and cut it into nearly two equal pieces. Suspend one of the pieces from the edge of a table with the help of a piece of thread Now hold the other piece of straw in your hand and rub its free end with a sheet of paper. Bring the rubbed end of the straw near the suspended straw. Make sure that the two pieces do not touch each other. What do you observe? Next, rub the free end of the suspended piece of straw with a sheet of paper. Again, bring the piece of straw that was rubbed
earlier with paper near the free end of the suspended straw. What do you observe now?
Picture
Answer: A straw rubbed with paper attracts another straw but repels it if it has also been rubbed with a sheet of paper. The force exerted by a charged body on another charged or uncharged body is known as electrostatic force.
Question 8. Take a transparent glass tube or a plastic pipe. The length of the pipe/tube should be about 15 cm and its diameter should be 5-7.5 cm. Also, take a piece of a thin sheet of good quality rubber, say, a rubber balloon. Stretch the rubber sheet tightly over one end of the pipe. Hold the pipe in the middle, keeping it in a vertical position. Ask one of your friends to pour some water into the pipe. Does the rubber sheet bulge out? Note also the height of the water column in the pipe. Pour some more water. Observe again the bulge in the rubber sheet and the height of the water column in the pipe. Repeat this process a few more times. Can you see any relation between the amount of the bulge in the rubber sheet and the height of the water column in the pipe?
Answer: The amount of bulge in the rubber sheet increases with the height of the water column in the pipe. Thus, the pressure exerted by water at the bottom of the container depends upon the height of its column.

Question 9. Take a plastic bottle. You can take a discarded water or soft drink bottle. Fix a cylindrical glass tube, a few cm long near its bottom You can do so by slightly heating one end of the glass tube and then quickly inserting it near the bottom of the bottle. Make sure that the
water does not leak from the joint. If there is any leakage, seal it with molten wax. Cover the mouth of the glass tube with a thin rubber sheet as you did it. Now fill the bottle up to half with water. What do you observe? Why does the rubber sheet fixed to the glass tube bulge this time? Pour
some more water into the bottle. Is there any change in the bulge’ of the rubber sheet? Answer: Yes, the rubber tube bulge out, and the bulging increases with the amount of water in the bottle. Thus, liquid exerts pressure on the walls of the container.

Question 10. Take an empty plastic bottle or a cylindrical container. You can take a used tin of talcum powder or a plastic bottle. Drill four holes all around near the bottom of the bottle. Make sure that the holes are at the same height from the bottom Now fill the bottle with water. What do you observe? Do the different streams of water coming out of the holes to fall at the same distance from the bottle? What does this indicate?
Answer: We observed different streams of a waterfall at the same distance from the bottle. Thus, it indicates that liquids exert equal pressure at the same depth.

Question 11. Take a good quality rubber sucker. It looks like a small rubber cup Press it hard on a smooth plane surface. Does it stick to the surface? Now try to pull it off the surface. Can you do it?

Answer: When we press the sucker, most of the air between its cup and the surface escapes. The sucker sticks to the surface because the pressure of the atmosphere acts on it. To pull the sucker off the surface, the applied force should be large enough to overcome the atmospheric pressure. Thus, this activity gives us an idea about the magnitude of atmospheric
pressure.

KSEEB Class 8 Force And Pressure Textbook Solutions 

Force And Pressure Additional Questions

Question 1. A ball of dough is rolled into a flat chapatti.
Name the force exerted to change the shape of the dough.
Answer: Muscular force

Question 2. Where do we apply a force while walking?
Answer: While walking we apply force on the ground.

Question 3. What is the name of the instrument used to measure atmospheric pressure?
Answer: Barometer

Question 4. Give two examples of contact force.
Answer: Muscular force, the force of friction.

Question 5. What kind of force is an electrostatic force?
Answer: Non-contact force

Question 6. What do you mean by magnitude?
Answer: The strength of a force is usually expressed by its magnitude.

Question 7. How do fluids exert pressure?
Answer: Fluids exert pressure in all directions. Fluids also exert pressure on the walls of the container that hold them.

Question 8. A force of 100 N is applied on an area of 4m² Compute pressure is applied on the area.
Answer: Given: Force = 100 N, Area = 4n²
Pressure = Force /Area =100/4 = 25pa.

Question 9. What is the similarity between electrostatic and magnetic forces?
Answer:

Both are non-contact forces.

Both are attractive as well as repulsive forces.

Question 10. What are the effects of force on an object?
Answer:

Force can change the state of motion of an object.

Force changes the speed of a moving object.

Force can cause an object to turn or change direction.

Force can change the shape of an object.

Question 11. State the difference between contact force and non-contact force.
Answer:
Contact force

The force that can be applied only when it is in contact with an object is called a contact force. Examples: muscular force, and frictional force.

Non-contact force

The force exerted on an object without touching it is known as non-contact force. Examples: gravitational force, and magnetic force.

Question 12. Why it is easier to walk on soft sand if we have flat shoes rather than shoes with sharp heels (or pencil heels)?
Answer: A flat shoe has a greater area in contact with the soft sand and exerts less pressure on the soft ground. Due to this, the flat’ shoes do not sink much in soft sand and it is easy to walk on them. On the other hand, a sharp heel has a small area in contact with the soft sand and exerts greater pressure on the sand. Due to this, the sharp heels sink deep into soft sand making it difficult for the wearer to walk on them.

Force And Pressure Class 8 KSEEB Exercise Solutions 

Force And Pressure Activity

Question 1. Take a tumbler and fill it with water. Cover the mouth of the tumbler with a thick card similar to that of a postcard. Hold the tumbler with one hand while keeping the card pressed to its mouth with your other hand. Turn the tumbler upside down while keeping the card pressed tots mouth. Make sure that the tumbler is held vertically. Gently remove the hand pressing the card. What do you observe? Does the card get detached allowing the water to spill? With a little practice, you will find that the card continues to hold water in the tumbler even after it is not supported by your hand. Also, try this activity by using a piece of cloth to hold the tumbler in an upside-down position.
Answer: Question 2. Make a 50cm x 50cm bed of dry sand about 10cm in thickness. Make sure that its top surface is leveled. Take a wooden or a plastic stool. Cut two strips of graph paper each with a width of 1 cm. Paste them vertically on any leg of the stool—one at the bottom and the other from the top. Now gently put the stool on the sand bed with its legs resting on the sand. Increase the size of the sand bed if required. Now put a load, say a school bag full of books, on the seat of the stool. Mark the level of sand on the graph strip. This would give you the depth, if any, to which the legs of the stool sink in the sand. Next, turn the stool upside down so that now it rests on its seat on the sand bed. Note the depth to which the stool sinks now. Next, put the same load on the stool and note the depth to which it sinks in the sand. Compare the pressure exerted by the stool in the two situations.
Answer: Pressure exerted by the stool is greatest in the first situation.

Multiple Choice Questions

Question 1. Two boys A and B are shown applying force on a block. If the block moves toward the right, which one of the following statements is correct?
1. The magnitude of force applied by A is greater than that of B.
2. The magnitude of force applied by A is smaller than that of B.
3. The net force on the block is towards A.
4. The magnitude of force applied by A is equal to that of B.
Picture
Answer: 1. Magnitude of force applied by A is greater than that of B.
Explanation: The magnitude of force applied by 1 is bigger than that of B as a result of the block moves towards the right i.e. towards 2.

Question 2. When the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of the hammer?
1. Gravitational force alone
2. Electrostatic force alone
3. Magnetic force alone
4. Frictional force alone

Answer: 3. Magnetic force alone
Explanation: As electric current flows through the coil it behaves like an electromagnet which creates magnetic force. Hence the answer is magnetic force alone.

Question 3. During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is
1. Force of gravity.
2. Electrostatic force.
3. The force of friction.
4. Magnetic force.
Answer: 2. Electrostatic force.
Explanation: On combing the hair, the comb and hair get oppositely charged due to electrostatic force.

Question 4. A container filled with water. Which of the following statements is correct about the pressure of water?
1. The pressure at A> Pressure at B > Pressure at C.
2. The pressure at A= Pressure at B = Pressure at C.
3. The pressure at A< Pressure at B > Pressure at C.
4. The pressure at A< Pressure at B.
Answer: 4. The Pressure at A< Pressure at B
Explanation: An increase in water leads to an increase in depth.

Question 5. Two objects repel each other. This repulsion could be due to
1. Frictional force only
2. Electrostatic force only
3. Magnetic force only
4. Either a magnetic or an electrostatic force
Answer: 4. Either a magnetic or an electrostatic force
Explanation: when two objects are experiencing repulsive force because there may be an electrostatic force or a magnetic force.

Important Questions For KSEEB Class 8 Force And Pressure 

Question 6. Which one of the following forces is a contact force?
1. Force of gravity
2. Force of friction
3. Magnetic force
4. Electrostatic force
Answer: 2. Force of friction
Explanation: Force of attraction acts only when the bodies are in contact.

Question 7. A water tank has four taps fixed at points A, B, C, and D in Fig. The water will flow out at the same pressure from the taps at
1. B and C
2. A and B
3. C and D
4. A and C
Answer: 1. B and C
Explanation: B and C are at the same level, hence pressure will be the same at B and C.

Question 8. A girl is pushing a box in the east direction. In which direction should her friend push the box so that it moves faster in the same direction?
Answer: Towards the east.

Question 9. In the circuit, when the key is closed, the compass needle placed in the matchbox deflects. Name the force which causes this deflection.
Answer: Magnetic force.

Question 10. During dry weather, clothes made of synthetic fiber often stick to the skin. Which type of force is responsible for this phenomenon?
Answer: Electrostatic force

Question 11. While sieving grains, small pieces fall down. Which force pulls them down?
Answer: Force of gravity.

Question 12. Does the force of gravity act on dust particles?
Answer: Yes, the force of gravity act on dust particles.

Question 13. A gas-filled balloon moves up. Is the upward force acting on it larger or smaller than the force of gravity?
Answer: The upward force is larger than the force of gravity.

Question 14. Does the force of gravitation exist between two astronauts in space?
Answer: Yes, the force of gravitation exists between two astronauts in space.

Question 15. A chapati maker is a machine that converts balls of dough into chapati. What effect of force comes into play in this process?
Answer: Force works on the dough to convert it to chapati.

Question 16. Shows a man with a parachute. Name the force which is responsible for his downward motion. Will he come down at the same speed without the parachute?
Answer: Force of gravity is responsible for his downward motion. If he comes down without a parachute his speed will be higher.

Question 17. Two persons are applying forces on two opposite sides of a moving cart. The cart still moves at the same speed in the same direction. What do you infer about the magnitudes and direction of the forces applied?
Answer: Force applied is of equal magnitude in the opposite direction hence the cart moves with the same speed in the same direction.

Question 18. Two thermocouple balls held close to each other move away from each other. When they are released, name the force which might be responsible for this phenomenon. Explain.
Answer: Two Thermocol balls held close to each other move away from each other, which is because of electrostatic force. The balls having similar charges move away due to repulsion between similar charges.

Question 19. Fruits detached from a tree fall down due to the force of gravity. We know that a force arises due to the interaction between two objects. Name the objects interacting in this case.
Answer: Earth and fruits.

Question 20. Aman is pushing a cart down a slope. Suddenly the cart starts moving faster and he wants to slow it down. What should he do?
Answer: He should apply force to pull the cart up the slope.

Question 21. Shows a car sticking to an electromagnet. Name the forces acting on the car. Which one of them is larger?

Answer:

Magnetic force (in the upward direction) force of gravity or the weight of the car (downward) act once.

Magnetic force is larger than the force of gravity.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions For Class 8 Science Chapter 4 Materials Metals and Non-Metals Points To Remember

Physical properties: Metals are

1. Malleable
2. Ductile
3. Good conductors of heat and electricity
4. Lustrous
5. Solids at room temperature except for mercury.
6. High melting and boiling points.
7. Hard except for sodium and potassium
8. Sonorous

Non-metals are:

1. Nonmalleable
2. Non – ductile
3. Bad conductors of heat and electricity
4. Non-lustrous
5. Generally solids and gases at room temperature
6. Have low melting and boiling points
7. Are soft except for diamond
8. Non – sonorous

Chemical properties :

1. Metal oxides are basic in nature, which turn red litmus blue
2. Non-metal oxides are acidic in nature, which turn blue litmus red
3. Metals react with water to produce metal hydroxide and evolve hydrogen gas.
4. Metals react with dilute acids forming a salt and evolving hydrogen gas.
5. The process where metal gets eaten away due to a chemical reaction with atmospheric gases and moisture is known as corrosion.
6. The arrangement of metals in the order of their decreasing reactivity is the reactivity series.
7. Graphite is used for making electrodes, cru- cables and pencil lead.
8. Phosphorus is used in the match stick industry and in fireworks
9. Sulphur is used in the vulcanisation of rubber
10. Copper and aluminium are used to make electrical wires.
11. Alloys are the mixtures of two or more metals or metals and non-metals.

Materials: Metals and Non-Metals Ncert Textbook Exercises

Question 1. Which of the following can be beaten into thin sheets?
1. Zinc
2. Phosphorus
3. Sulphur
4. Oxygen
Answer: 1. Zinc

Question 2. Which of the following statements is correct?
1) All metals are ductile
2) All non-metals are ductile
3) Generally, metals are ductile
4) Some, non-metals are ductile
Answer: 3) Generally, metals are ductile

Question 3. Fill in the blanks :
(1) Phosphorusisavery_____non-metals.
(2) Metals are ______ conductors of heat and _______
(3) Iron is _______ reactive than copper.
(4) Metals react with acids to produce ______ gas.
Answer:
(1)Reactive
(2) Good, Electricity
(3) More
(4) Hydrogen

Question 4. Mark ‘T” if the statement is true and ‘F’ if it is false.
(1) Generally, non-metals react with acids.
(2) Sodium is a very reactive metal.
(3) Copper displaces zinc from zinc sulphate
(4) Coal can be drawn into wires.
Answer:
(1) False
(2) True
(3) False
(4) False

Class 8 Science KSEEB Materials Metals And Non-Metals notes 

Question 5. Some properties are listed Distinguish between metals and non-metals on the basis of these properties.
Answer:
Properties
1. Appearance
2. Hardness
3. Malleability
4. Ductility
5. Heat Conduction
6. Conduction of electricity
Metals
1. Lustrous
2. Hard
3. Malleable
4. Ductile
5. Good Conductors
6. Good
Non-metals
1. Dull
2. Soft
3. Non-malleable
4. Non-ductile
5. Bad conductors
6. Bad conductors

Question 6. Give reasons for the following
1)Aluminium foils are used to wrap food items.
Answer: Because aluminium metal is malleable and therefore, it can be beaten into thin foils.

2) Immersion rods for heating liquids are made up of metallic substances.
Answer: Because metals are good conductors of heat and electricity.

3) Copper cannot displace zinc from its salt. solution.
Answer: Because copper is less reactive than zinc.

4) Sodium and potassium are stored in kerosene.
Answer: Because they are highly reactive elements and can catch fire easily when in contact with air.

Question 7. Can you store the lemon pickles in an aluminium utensil? Explain.
Answer: Lemon pickle cannot be stored in aluminium utensils because lemon pickle contains acids, which can react with aluminium (metal) liberating hydrogen gas, and can lead to the spoiling of the pickle.

Question 8. Match the substances in column A with their applications given in column B
Column A                             Column B
(substance)                         (Application)
Gold                                 (1) Thermometer
Iron                                  (2) Electric wires
Aluminium                      (3) Wrapping food
Carbon                            (4) Jewellery
Copper                            (5) Machinery
Mercury                          (6) Fuel

Answer: Gold-(4) Jewellery
Iron-(5) Machinery
Aluminium-(3) Wrapping food
Carbon -(6) Fuel
Copper -(2) Electric wires,
Mercury-(1) Thermometer

Question 9. What happens when
1) Dilute sulphuric acid is poured on a copper plate?
2) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Answer:
1) No reaction will take place because copper is very less reactive.
2) Iron being more reactive displaces copper from the copper sulphate solution. In this reaction, the blue colour of copper sulphate fades and there is a deposition of copper on the iron nail.
Iron + Copper sulphate — Iron sulphate + copper

Question 10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
1) How will she find the nature of the gas?
2) Write down the word equations of all the reactions taking place in this process.
Answer: 1) Saloni can find the nature of the gas by using a wet litmus paper. After bringing the litmus paper in contact with the gas, if it turns the blue litmus paper into red, it is acidic, and if it turns red litmus into blue, it is basic.

2) Carbon + Oxygen — Carbon dioxide Carbon dioxide + lime water — Milky
or
Carbon dioxide + water — carbonic acid (Blue litmus red)

KSEEB Class 8 Science Chapter 4 Important Questions 

Question 11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. The next day, when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Answer: The gold jewellery is dipped into an acidic solution called aquaria (a mixture of hydrochloric acid and nitric acid) for polishing. On dipping the gold jewellery in the acid solution, the outer layer of gold dissolves and the inner shiny layer appears. This causes a slight loss in weight.

Materials: Metals and Non-Metals Activities

Take a small iron nail, a coal piece, a piece of thick aluminium wire and a pencil lead. Beat the iron nail with a hammer
(But take care that you don’t hurt yourself in the process). Try to hit hard. Hit hard the aluminium wire also. Then repeat the same kind of treatment on the coal piece and pencil lead. Record your observations Malleability of Materials
Object/Material                                          Change in Shape
Iron wall Flattens                                       (Flattens/Breaks into Pieces)
Coal piece                                                   Breaks into pieces
Aluminium wire                                         Flattens
Pencil lead                                                  Breaks into pieces
Answer: This activity shows that iron and aluminium are malleable while coal pieces and pencil lead are brittle. Thus, metals are malleable and non-metals are non-malleable.

Question 2. Recall how to make an electric circuit to test whether electricity can pass through an object or not.

You might have performed the activity with various objects in Class VI. Now, repeat the activity with the materials mentioned Observe and group these materials into good conductors and poor conductors.

Materials                                             Good Conductor/Poor Conductor
Iron rod/nail                                       Good conductor
Sulphur                                               Poor conductor
Coal piece                                           Poor conductor 
Copper wire                                        Good conductor
Answer: It shows that metals are good conductors of electricity and non-metals are poor conductors of electricity.

Question 3. Let us check the nature of rust formed as a result of the reaction between iron, oxygen and water. Collect a spoonful of rust and dissolve it in a very little amount of water. You will find that the rust remains suspended in water. Shake the suspension well. Test the solution with red and blue litmus papers, What do you observe? Is the solution acidic or basic?

Answer: We observed that the red litmus paper turns blue which shows that the injury of rust is basic. Blue litmus paper does not show any colour change with the solution.

KSEEB Class 8 Science Solutions For Materials Metals And Non-Metals 

Question 4. (To be demonstrated by the teacher in the (class)
Take a small amount of powdered sulphur in a deflagrating spoon and heat it. If the deflagrating spoon is not available, you may take a metallic cap of any bottle and wrap a metallic wire around it and give it the shape.
As soon as sulphur start burning, introduce the spoon into a gas jar/glass tumbler. Cover the tumbler with a lid to ensure that the gas produced does not escape. Remove the spoon after some time. Add a small quantity of water into the tumbler and quickly of water into the tumbler and quickly replace the lid. Shake the tumbler well. Check the solution with red and blue litmus papers.

Answer: We observed that the solution of oxide turns the blue litmus red which shows that the solution is acidic in nature. This also shows that the oxide of non-metals is acidic in nature.

Question 5. Take a 250 ml. beaker/glass tumbler. Fill half of it with water. Now carefully cut a small piece of sodium metal. Dry it using filter paper and wrap it in a small piece of cotton. Put the sodium piece wrapped in cotton into the beaker. Observe carefully.
When the reaction stops, touch the beaker. What do you feel? Has the beaker become hot? Test the solution with red and blue litmus papers. Is the solution acidic or basic?
Answer: On touching the beaker, it felt hot. The solution turns the red litmus paper to blue which shows it is basic in nature. Blue litmus paper does not show any colour change with the solution.

Question 6. Take samples of metals and non-metals given in separate test tubes and label them as A, B, C, D, E and F. With the help of a dropper add 5 mL of dilute hydrochloric acid to each test tube one by one. Observe the reactions carefully. If no reaction occurs in the cold solution, warm the test tube gently. Bring a burning matchstick near the mouth of each test tube. Repeat the same activity using dilute sulphuric acid instead of dilute hydrochloric acid.

The reaction of Metals and Non-metals with Acids

Answer: This activity shows that metals usually displace hydrogen from dilute acids whereas non-metals do not do so and no hydrogen gas is evolved.

Question 7. Prepare a fresh solution of sodium hydroxide in a test tube by dissolving 3-4 pellets of it in 5 mL of water. Drop a piece of aluminium foil into it. Bring a burning matchstick near the mouth of the test tube. Observe carefully.
Answer: We observed that a colourless gas is evolved which burns with a pop sound. This shows that aluminium reacts with bases on heating to produce hydrogen gas.

Question 8. Take five 100 mL beakers and label them A,B, C, D and E. Take about 50 mL of water in each beaker. Dissolve in each beaker a teaspoonful of each substance as indicated
(1) Keep the beakers undisturbed for some time
(2) Record your observations in your notebook.

Picture

Beaker A: Copper sulphate (CuSO₄) + Zinc granule (Zn)
Beaker B: Copper sulphate (CuSO₄) + Iron nail (Fe)
Beaker C: Zinc sulphate (ZnSO₄) + Copper turnings (Cu)
Beaker D: Iron sulphate (FeSO₄) + Copper turnings (Cu)
Beaker E: Zinc sulphate (ZnSO₄) + Iron nail(Fe)

Answer: In beaker ‘A’ zinc (Zn) replaces copper (Cu) with copper sulphate (CuS04) solution. That is why the blue colour of copper sulphate changes to colourless and a powdery red mass of copper is deposited at the bottom of the beaker. The reaction can be represented as follows:

In beaker B, iron replaces copper from its solution. That is why the blue colour of copper sulphate changes to the green colour of ferrous sulphate.

In beakers C, D and E no change in colour or heat evolution is observed. This indicates that the metals are unable to displace the other metals from their solution.

Materials: Metals and Non-Metals Additional Questions

Question 1. Examples of metals.
Answer: Iron, sodium, aluminium

Question 2. Examples of nonmetals.
Answer: Sulphur, oxygen, hydrogen

Question 3. Name two soft metals
Answer: Sodium, potassium.

Question 4. Which non-metal is essential for our life and all living beings inhale during breathing?
Answer: Oxygen

Question 5. Which property of metals makes them suitable for use in jewellery?
Answer: Ductility

Materials Metals And Non-Metals Class 8 KSEEB Questions And Answers 

Question 6. Define malleability
Answer: The property of metals by which they can be drawn into thin sheets.

Question 7. Which liquid metal is used for making thermometers?
Answer: Mercury

Question 8. What do you understand by a displacement reaction? Give example.
Answer: A chemical reaction in which a more reactive metal displaces a less reactive metal from its salt solution.
Ex: CuSO, +Fe — FeSO, + Cu

Copper sulphate + Iron — Iron sulphate + Copper

Question 9. What is rust?
Answer: Reddish brown coating that is formed on iron objects on exposure to moist air.

Question 10. Name the metal and non-metal which occur in a liquid state.
Answer: Mercury (metal), bromine (non-metal).

Question 11. Due to which property a bell rings?
Answer: Sonority

Simplified Notes For KSEEB Class 8 Science Metals And Non-Metals 

Question 12. State the property of non-metals due to which phosphorus is kept in water.
Answer: Non-metals do not react with water.

Question 13. Which metal is used for wrapping food items?
Answer: Aluminium

Question 14. Whose oxides are basic in nature: Metal or non-metal?
Answer: Metal

Question 15. What are the main uses of metals?
Answer: Metals are very useful to us in many ways. For example:

1. Due to their thermal and electrical conductivity, metals are used to make utensils, cooking vessels, wires and appliances. For example, copper and aluminium are mainly used for these purposes.
2. Metals like iron and steel are used in various tools, machinery, pipes, rods, sheets, doors, windows, and construction works like bridges, roads, buildings, etc.,
3. Aluminium is used as packaging and wrapping materials. It is also used in aircraft and automobiles, etc.
4. Metals like gold, silver and platinum are used to make jewellery and other decorating items.
5. Zinc is used in galvanisation and dry cell and chromium in electroplating.
6. Lead is used in making electrodes and batteries.

Question 16. What are the main uses of non-metals?
Answer: Like metals, non-metals also play an important role in our lives. They help us in many ways. For example

1. We breathe oxygen which is the basis of life for all living things including human beings. Without it, no living beings can exist alive on this earth.
2. CO2, which is a non-metal oxide is essential for plants to carry out photosynthesis.
3. Non-metals like nitrogen and phosphorus are used in fertilisers for better yield of plants.
4. Phosphorus is used in the manufacturing of matchsticks and fireworks.
5. Non-metal-like iodine is used in the purple-coloured solution applied on wounds. Sulphur is also used in preparing skin medicines and making ointments due to its fungicidal properties.
6. Non-metal-like chlorine is used in the water purification process. Due to its bleaching properties, it is used to make bleaching powder.
7. Carbon, a non-metal, is used in most the fuels

Materials: Metals and Non-Metals Multiple Choice Questions

Question 1. Which of the following is not a metal?
(1) Copper
(2) Sulphur
(3)Aluminium
(4) Iron
Answer: (2) Sulphur

Question 2. The substance that will be flattened on beating with a hammer is
(1) Crystalofiodine
(2) Lump of sulphur
(3) Piece of coal
(4) Zine granule
Answer: (4) zinc granule
Explanation: Metals can be beaten into thin sheets whereas non-metals break into pieces on hitting hence answer is (d) zine granule.

Question 3. Boojho has learnt that non-metals on beating with a hammer are generally broken into pieces. Which of the following is a nonmetal?
(1) Iron nail
(2) Aluminium wire
(3) Copperplate
(4) Piece of coal
Answer: (4) Piece of coal
Explanation: Iron, Copper and aluminium are metals whereas coal is a non-metal hence answer is (d) a piece of coal.

Question 4. Materials which can be drawn into wires are called ductile. Which of the following is not a ductile material?
(1) Silver
(2) Copper
(3) Sulphur
Answer: (3) sulphur
Explanation: Ductility is the property of metals. Here Sulphur is non-metal which is not have ductile properties.

Question 5. Metals are generally hard. Which of the following metals is an exception and can be cut with a knife?
(1) Iron
(2) Sodium
(3) Gold
(4) Magnesium
Answer: (2) Sodium
Explanation: Sodium is a highly reactive metal which looks soft and can be cut into pieces by using a knife.

Question 6. Metals are generally solid. Which of the following metals is in the liquid state at room temperature?
(1) Mercury
(2) Silver
(3)Aluminium
(4) Sodium
Answer: (1) Mercury

Question 7. Metals generally react with dilute acids to produce hydrogen gas. Which one of the following metals does not react with dilute hydrochloric acid?
(1) Magnesium
(2) Aluminium
(3) Iron
(4) Copper
Answer:(4) Copper
Explanation: Less reactive metals like Copper, gold and silver does not react with dilute HCl to produce Hydrogen gas.

Explanation Of Metals And Non-Metals In KSEEB Science 

Question 8. Which of the following reacts with cold water vigorously?
(1) Carbon
(2) Sodium
(3) Magnesium
(4) Sulphur
Answer:(2) Sodium
Explanation: Sodium reacts vigorously with water, hence it is stored in kerosene to avoid the reaction of sodium with moisture in the atmosphere and oxygen.

Question 9. The metal which produces hydrogen gas in reaction with dilute hydrochloric acid as well as sodium hydroxide solution is
(1) Copper
(2) Iron
(3) Aluminium
(4) Sodium
Answer:(3) Aluminium
Explanation: Aluminium reacts with dilute HCI as well as NaOH to produce Hydrogen Gas.

Question 10. Which of the following non-metals reacts and catches fire on exposure to air?
(1) Phosphorus
(2) Nitrogen
(3) Sulphur
(4) Hydrogen
Answer: (1) Phosphorus

Question 11. Generally, metallic oxides are basic and nonmetallic oxides are acidic in nature. The solution of which of the following oxides in water will change the colour of blue litmus to red?
(1) Sulphur dioxide
(2) Magnesium oxide
(3) Iron oxide
(4) Copper oxide
Answer: (1) Sulphur dioxide
Explanation: Sulphur forms Sulphur-di-oxide which is acidic in nature and it will convert blue litmus to red.

Question 12. Which of the following property is not responsible for copper being used as electrical conduction wires?
(1) Ductility
(2)Colour
(3) Good conductor of electricity
(4) It is solid
Answer : (2) Colour.

Question 13. Name two major non-metals which are present in fertilisers and enhance the growth of plants.
Answer: (1) Nitrogen (2) Phosphorus

Question 14. Which non-metal is used to disinfect water?
Answer: Chlorine.

Question 15. A purple-coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the nonmetal.
Answer: Iodine.

Question 16. Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it?
Answer: There will be no change as displacement reaction will not take place.

Question 17. Why are bells made of metals?
Answer: Metals show the sonorous property, hence they are used in making bells.

Question 18. Paheli bought a statue made of copper. To her surprise, it acquired a dull green coating after a couple of months. Explain the reason.
Answer: The green coating on the copper statue is a mixture of Cu(OH), and CuCO, which are formed due to the reaction of moisture and copper.

Question 19. Some of the following statements are incorrect. Find the incorrect statements and correct them.
(1) The property of metals by virtue of which they can be drawn into wires is called ductility.
(2) Metals are good conductors of electricity but poor conductors of heat.
(3) Articles made of metals produce a ringing sound when struck hard.
(4) Oxides of non-metals and metals are acidic in nature.
(5) A less reactive metal replaces a more reactive metal from its salt solution in water.

Answer: Statements 2), 4) and 5) are wrong statements
2) Metals are good conductors of electricity as well as heat.
4) Oxides of non-metals are acidic in nature and oxides of metals are basic in nature.
5) Amore reactive metal replaces a less reactive metal from its salt solution in water.

20. Match the substances in Column A with their applications given in Column B.
Column A (Substance)             Column B (Application)
Oxygen                                       for making crackers
Copper                                        for disinfecting water
Sulphur                                       all living beings inhale during breathing
iron                                             for making electric wires

Answer:
Column A(Substance)               Column B(Application)
Oxygen                                      all living beings inhale during breathing
Copper                                       for making electric wires
Sulphur                                      for making crackers
Iron                                            for making rails
chlorine                                     for disinfecting water

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water Points To Remember

Pollution: An undesirable change in the physical, chemical or biological characteristics of air, water and land that may be harmful to human life and other animals living conditions, industrial processes and cultural assets.

Pollutants: The agents that pollute our environment are called pollutants.
Pollutants are the substances which contaminate air, water, and land, For eg. smoke, dust fog and gases like sulphur dioxide and nitrogen dioxide. Air pollution is the contamination of air by impurities which may have a harmful impact on living organisms and non-living components.

Sources of Air Pollution:

Natural Sources: Smoke and dust arising from forest fires or volcanic eruptions. Methane gas arising from decaying organic matter, Man-made

Sources: Exhaust gases from factories, power plants and automobiles.

Carbon monoxide, nitrogen oxides, carbon dioxide, methane and sulphur dioxide are the major pollutants in the air. Smog is a mix in air of smoke and chemicals with fog. The chemical components of smog can include ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide. Smog can trigger breathing difficulties like asthma and coughing.

Steps to prevent air pollution:
Use of fuels like CNG and unleaded petrol in automobiles. Switching to alternative fuels, like solar energy, hydropower and wind energy.
Planting trees. Travelling to school on a bicycle or on public transport or carpooling. Avoiding the burning of leaves, trash and vegetable matter Restricting cigarette smoking. Increasing levels of greenhouse gases like CO, and CEC (Chlorofluorocarbon) are leading to global warming. Excessive use of CFCs damages the ozone layer which protects the earth from harmful UV rays emitted by the sun.

Greenhouse Effect and Global Warming:
The sun’s rays warm the earth’s surface. A part of the radiation that falls on the earth is absorbed by it and a part is reflected back into space. A part of the reflected radiation is trapped by the atmosphere due to the presence of gases like water vapour, carbon dioxide, methane, nitrous oxide etc known as greenhouse gases. This is known as the greenhouse effect.

The trapped radiations further warm the earth and have adverse effects such as the melting of glaciers and increasing sea levels. This phenomenon is
known as global warming.

Water pollution is the contamination of water by objectionable and harmful substances such as sewage, toxic chemicals, silt etc.

Sewage, agricultural chemicals and industrial waste are some of the major contaminants of water.

Water which is purified and fit for drinking is known as potable water. Water is a precious natural resource. We must learn to conserve it.

Class 8 Science KSEEB Pollution of Air and Water Notes 

Pollution Of Air And Water NCERT Textbook Exercises

Question 1. What are the different ways in which water gets contaminated?
Answer: Water gets contaminated due to the addition of substances harmful to health. Sewage, agricultural chemicals and industrial wastes are some of the major contaminants of water.

Question 2. At an individual level, how can you help reduce air pollution?
Answer: At an individual level we can help in reducing air pollution by following methods:
1. We can plant trees and nurture the ones already present in the neighbourhood.
2. We can take part in Van Mahotsava actively and effectively every year and motivate people about the importance of plantation.
3. We can educate people against burning dried leaves and plants and advise them to put them in a compost pit.

Question 3. Clear, transparent water is always fit for drinking. Comment
Answer: No clear and transparent water even without smell, may contain bacteria, viruses etc. which are not visible to the eyes. Drinking such water can cause illnesses of various kinds. Therefore, we must drink purified and potable water after boiling.

Question 4. You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Answer: The following steps could be taken:
1. First of all procurement of the required amount of water for all residents should be ensured.
2. Wastage of water by leakage at various places should be taken into account.
3. Water treatment should be ensured.
4. Must have sufficient water tanker to meet emergency situations.

Question 5. Explain the differences between pure air and polluted air.
Answer: Pure air is free from any pollutants has no smell, is soothing and not irritating to the eyes. Whereas polluted air gives a filthy smell and people cannot breathe in it. If people inhale such air, they may suffer from various breathing, heart and lung problems. Even sometimes people die from inhaling polluted air.

Question 6. Explain the circumstances leading to acid rain. How does acid rain affect us?
Answer: Gases like sulphur dioxide and nitrogen dioxide react with water vapour present in the atmosphere to form Sulphuric acid and nitric acid. These acids come down with rain water, making the rain acidic. This is known as acid rain. Acid rain corrodes the marble of the monuments. This phenomenon is known as Marble Cancer. It also kills the useful organism in agricultural soil.

Question 7. Which of the following is not a greenhouse gas?
1. Carbon dioxide
2. Sulphur dioxide
3. Methane
4. Nitrogen
Answer: 2. Sulphur dioxide.

Question 8. Describe the ‘Green House Effect’ in your own words.
Answer: The Sun’s rays when fall on the earth’s surface, get warm. Some of the Sun’s rays are trapped by the atmosphere and these and not allowed to go out of the earth’s atmosphere. This trapped heat cause warming of the atmosphere called the greenhouse effect. The gases like methane and carbon dioxide form a thick layer and prevent the escaping of heat causing this effect. Due to the greenhouse effect, global warming is happening.

Question 9. Prepare a brief speech on global warming. You have to deliver the speech in your class.
Answer:
1. Today, global warming has appeared as one of the most severe threats to human beings. On one hand, carbon dioxide is added to the atmosphere due to human activities. On the other hand, the forest area is decreasing day by day. It leads to an increase in the amount of carbon dioxide in the atmosphere. The accumulation of this gas causes the greenhouse effect and global warming.
2. Global warming can create the melting of ice of icebergs, resulting in a rise in the sea level and causing the flooding of many coastal areas. So, we must be aware of this problem and take every possible step to tackle it

Question 10. Describe the threat to the beauty of the ‘TajMahal
Answer: The Taj Mahal is made of white marble which is getting affected adversely due to the industrial pollutants from Agra, Mathura etc. the sulphur dioxide gas along with nitrogen oxide gas released from these industries mix with rainwater to form Sulphuric acid that falls on the marble of this monument. The acid rain corrodes the marble and makes it yellowish. This is a matter of great concern that world-famous monument like the Taj Mahal may get damaged due to the pollutants emitted by factories
around it.

Question 11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer: Agriculture relies on the use of chemical fertilizers to improve crop yield. All these chemicals dissolve in water and run into water bodies from the fields. These seep into the ground and pollute the groundwater. A lot of algae in the ponds grow and keep the ponds green. This is caused due to excessive quantities of chemicals like nitrates and phosphorous present in fertilisers. Excessive growth of algae decreases the oxygen level at water bodies and kills the other aquatic animals living inside it.

KSEEB Class 8 Science Solutions For Pollution of Air And Water 

Pollution Of Air And Water Activities

Question 1. You may have covered your nose while passing a brick kiln emitting smoke or started coughing while walking on a busy road

On the basis of your experience, compare the quality of air at the places given below: A park and a busy road.
A residential area and an industrial area.
A busy traffic intersection at different times of the day, e.g., early morning, afternoon and evening.
A village and a town.
Answer: When we visit a park we find it full of fresh air and on a busy road we find it polluted due to fumes, smoke, dust and sound.
An industrial area is more polluted as compared to a residential area as an industrial area gets polluted with chemical pollutants, toxic gases, etc. Early morning there is less pollution but in the afternoon it becomes a little more polluted than in the morning and in the evening it becomes extremely polluted. A town is more polluted than a village.

Question 2. Prepare a table using the pollutants mentioned above You may even add more data to the following Table
Answer:

Question 3. You have various options of commuting to your school such as walking, going by bicycle, travelling by bus or other public transport, using a car individually, travelling by carpool. Discuss in your class the impact of each of these options on the quality of air.
Answer:

Question 4. Try to collect samples of water from a tap, pond, river, well and lake. Pour each into separate glass containers. Compare these for smell, acidity and colour. Complete the following Table.
Answer:

Question 5. You investigated the sewage disposal system of your locality in Class VII. Do you remember how the sewage was collected from your home and where it went thereafter?
Answer: The underground network of small and big pipes called sewers carry the sewage from the point of production to the point of disposal, i.e., the treatment plant.

Question 6. Let us construct a water filter with simple, everyday materials.
Take a plastic bottle and cut it into 2 halves at the centre. Use the upper half as a funnel by putting it upside down in the lower half. Make layers in it with a paper napkin or a fine cloth followed by, cotton, sand and then gravel. Now pour dirty water through the filter and observe the filtered water.
Discuss the following questions amongst yourselves and with your teacher:
Why do we need to filter water before drinking?
Where do you get your drinking water from?
What will happen if we drink polluted water?
Answer:
1. Water which is full of dust particles and impurities is unfit for human health thus we need to filter water before drinking it.
2. We get drinking water from the government supply water or hand pump.
3. Polluted water has disease-carrying microorganisms and dissolved impurities which can make us seriously ill.

Pollution Of Air And Water Class 8 KSEEB Questions And Answers 

Pollution Of Air And Water Additional Questions

Question 1. What is the full form of CFC?
Answer: CFC — Chloro fluoro carbons

Question 2. What is meant by air pollution?
Answer: The presence of unwanted substances in the air which have a harmful effect on living and non-living components is known as air pollution.

Question 3. What name is given to unwanted substances present in the air?
Answer: Air pollutants.

Question 4. What are the harmful effects of smog?
Answer: Smog Causes breathing diseases such as asthma, cough and wheezing in children.

Question 5. How are CFCs added to the atmosphere?
Answer: CFCs are released from aerosol sprays, refrigerators and air conditioners.

Question 6. Name one important monument which has been affected by air pollution.
Answer: Taj Mahal is located in Agra.

Question 7. Expand SPM..,
Answer: Suspended Particulate Matter.

Question 8. Name some greenhouse gases.
Answer: Carbon dioxide, methane, nitrous oxide and water vapour.

Question 9. What is meant by polluted water?
Answer: Whenever substances such as sewage, toxic chemicals, silt, etc. which are harmful to life, get mixed with water, the water is said to be polluted.

Question 10. What is potable water?
Answer: Water which is suitable for drinking is called potable water.

Question 11. What is rain mixed with sulphuric acid called?
Answer: Acid rain.

Question 12. Name two smokeless fuels.
Answer: LPG and CNG.

Question 13. Name three diseases caused by polluted water.
Answer: Diarrhoea, dysentery and jaundice.

Question 14. What is Marble Cancer”?
Answer: Due to the acid rain the marble of the Taj Mahal has become yellow and is degrading. This is known as Marble Cancer”.

Question 15. Why is the greenhouse effect called so? How does it cause global warming?
Answer: It is called so because the earth’s atmosphere acts like a greenhouse made of glass in which sunlight enters through the transparent glass but the heat released by plants m the form of infrared radiation is not allowed to escape. Carbon dioxide does not allow heat to escape causing global warming.\

Explanation Of Pollution Of Air And Water In KSEEB Science 

Pollution Of Air And Water Multiple Choice Questions

Question 1. Air is a mixture of various gases. One of the gases is 21% part of the air and is essential for the survival of human beings. This gas is
1. Nitrogen
2. Oxygen
3. Ozone
4. Argon
Answer: 2. oxygen
Explanation: Nitrogen-78.09%
Ozone-0.000004%
Argon- 0.93%

Question 2. Which of the following is not a source of air pollution?
1. Automobile exhaust
2. Burning of firewood
3. Windmill
4. Power plant
Answer: 3. Windmill
Explanation: Windmill will not release any sort of gas into the atmosphere hence it is not considered a source of air pollution.

Question 3. Boojho wishes to contribute to reducing air pollution. Which vehicle should he use for going to school?
1. Car
2. School bus
3. Autorickshaw
4. Scooter
Answer: 2. School bus
Explanation: School buses carry many students hence reducing the emission. This will reduce air pollution.

Question 4. Which of the following is not a way to conserve water?
1. Replace
2. Reduce
3. Reuse
4. Recycle
Answer: 1. Replace
Explanation: Reduce, reuse and recycle is the formula to conserve natural resources. Replacement is not the way to conserve water.

Question 5. The type of pollution which is likely to affect the Taj Mahal in Agra to a greater extent is
1. Air pollution
2. Water pollution
3. Soil pollution
4. Noise pollution
Answer: 1. Air pollution
Explanation: Air pollution caused by residues from the nearby factory is causing damage to Tajmahal by converting white marble to yellow.

Question 6. Incomplete combustion of fuel such as petrol and diesel gives
1. Nitrogen oxide
2. Sulphur dioxide
3. Carbon monoxide
4. Carbon dioxide
Answer: 3. Carbon monoxide

Question 7. The phenomenon of marble cancer is due to
1. Soot particles
2. CFCs
3. Fog
4. Acid rain
Answer: 4. Acid rain
Explanation: Marble cancer is the phenomenon of corrosion of buildings and monuments due to the effect of acid rain.

Question 8. Potable water is the water which is
1. Obtained from a river.
2. Obtained from a lake.
3. Pure and fit for drinking.
4. Used only for washing clothes.
Answer: 3. Pure and fit for drinking.

Question 9. Which of the following procedures will give you water free from all impurities?
1. Adding chlorine tablets
2. Distillation
3. Boiling
4. Filtration
Answer: 2. Distillation

Question 10. A pond contains clean water. Which of the following activities will produce the least pollution of water?
1. Washing clothes in the pond
2. Animals bathing in the pond
3. Washing motor vehicles in the pond
4. Swimming in the pond.
Answer: 4. Swimming in the pond.

Question 11. Trees help in reducing the pollution of our environment. Lakhs of trees are planted by people in the month of July every year. The occasion is called
1. Forest Conservation Day
2. Plantation month
3. Van Mahotsav
4. wildlife week
Answer: 3. Van Mahotsav

Question 12. Which of the following is not a greenhouse gas?
1. Nitrogen gas
2. Water vapour
3. Methane gas
4. Carbon dioxide
Answer: 1. Nitrogen gas
Explanation: A gas that contributes to the greenhouse effect by absorbing infrared radiation is known as a greenhouse gas. Nitrogen is a part of atmospheric gases and it will not contribute to the greenhouse effect.

Question 13. Name the chemicals which are used in refrigerators and air conditioners and damage the ozone layer when released in the air.
Answer: Chlorofluorocarbons.

Question 14. Name any two sources which cause air pollution due to suspended particulate matter.
Answer:
1. Combustion of fuel
2. Industrial activities

Question 15. Name two gases which are mainly responsible for acid rain.
Answer:
1. Sulphur dioxide
2. Nitrogen dioxide

Question 16. The quality of air at various locations is monitored regularly by the government and other agencies? In what way can you use these data?
Answer: These data can be used to generate awareness about air pollution among people.

Question 17. The combustion of fossil fuels generates a lot of air pollution. Can you suggest any two alternative sources of energy which do not cause any pollution?
Answer: Solar energy and wind energy.

Question 18. Name any two water pollutants which are toxic for plants and animals.
Answer: Lead and Arsenic

Question 19. A lot of dry leaves are collected in a school garden and are burnt every day. Do you think that it is right to do so? If not, what should be done to dispose off the dry leaves?
Answer: Burning dry leaves is not the right thing to do as it causes air pollution. Converting dry leaves is the right thing to do as it does not cause any pollution and also gives manure.

Question 20. The level of air pollution is higher at a busy traffic intersections. Why?
Answer: Explanation: At traffic intersection automobiles stop for a while which lead to the accumulation of harmful gases at the junction. Hence the level of air pollution is higher at a busy traffic intersections.
Flow Chart

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current Point To Remember

Materials through which electric current can pass easily are called conductors of electricity. Electrical conductivity is a measure of the ability of a substance to allow the flow of an electric current.

Among solids, metals and graphite are good conductors of electricity and have high electrical conductivity. Some liquids are also good conductors. Pure water or distilled water is a poor conductor of electricity. But the presence of even a small amount of impurities(salts and minerals) makes water a good conductor as it contains ions through which conduction takes place.

Hence water from taps, wells, ponds, rivers, seas, lakes, etc. conducts electricity as they contain impurities. Most liquids that conduct electricity are solutions of acids, bases, and salts. When electricity is passed through a conducting solution, the molecules of the solution dissociate into ions. Ions are atoms or groups of atoms with a positive or negative charge.

These ions cause electrical conduction through the liquid. A liquid that conducts electricity due to the presence of ions is called an electrolyte.

Electrolysis:
1. The process of decomposition of a chemical compound in a solution when an electric current passes through it is called electrolysis. This process is due to the chemical effect of electric current.
2. Two electrodes are inserted in the solution and are connected to the terminals of a battery with a switch in between. This arrangement is called an electrolytic cell.
3. The electrode that is connected to the positive terminal of the battery is called the anode, and the other connected to the negative terminal is called the cathode.
4. Electrolysis is used in refining and extraction of metals from impure samples. This process is called electrorefining. It is also useful in coating one metal with another This process is called electroplating.
5. The passage of an electric current through a conducting solution causes chemical reactions. This is known as the chemical effect of electric current.

Some of the chemical effects of electric current are the following:
1. Formation of bubble of gas on the electrodes
2. Deposition of metal on electrodes
3. Change in colour of solutions

Electroplating:
1. The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
2. The object to be electroplated is made the cathode (negative electrode) by connecting it to the negative terminal of the battery.
3. The metal which has to be deposited is made the anode (positive electrode) by connecting it to the positive terminal of the battery. The electrolyte is usually a salt solution of the metal to be coated.

Application of Electroplating:
1. Metals that rust are often coated with other metals to prevent rusting.
2. Chromium plating is found on bath taps car bumpers, etc. to give a bright attractive appearance and resist scratches and wear.
3. Silver plating is done on cutlery and jewellery items.
4. Tin cans, used for storing food, are made by electroplating tin onto the iron. Tin is less reactive than iron. Thus, food does not come into contact with iron and is protected from getting spoilt.

Class 8 Science KSEEB Chemical Effects Of Electric Current Notes 

Chemical Effects Of Electric Current NCERT Text Book Exercises

Question 1. Fill in the blanks.
1. Most liquids that conduct electricity are solutions of _____,_____and ____.
2. The passage of an electric current through a solution causes effects.
3. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the _____ terminal of the battery.
4. The process of depositing a layer of any desired metal on another material by means of electricity is called _____

Answer:
1. Most liquids that conduct electricity are solutions of acids, bases and salts.
2. The passage of an electric current through a solution causes chemical effects.
3. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
4. The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.

Question 2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer: Yes, it is because the solution conducts electricity and the solution plays the role of the cell.

Question 3. Name three liquids, when tested in a manner that may cause the magnetic needle to deflect.
Answer: It may be the salt solution in water.

Question 4. The bulb does not glow in the setup List the possible reasons. Explain your answer?

Answer: The possible reasons are:
1. The solution may be conducting electricity but the current produced is too small so that the filament of the bulb does not get heated and the bulb does not glow.
2. It is possible that the connections are loose.
3. The cells are used up.

Question 5. A tester is used to check the conduction of electricity through two liquids. labelled A and B. it is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. you would conclude that
1. Liquid A is a better conductor than liquid B
2. Liquid B is a better conductor than liquid A
3. Both liquids are equally conducting
4. Conducting properties of liquid cannot be compared in this manner.
Answer:
1. Liquid A is a better conductor than liquid B.

Question 6. Does pure water conduct electricity? If not, what can we do to make it conduct?
Answer: No. Pure water does not conduct electricity. This is because pure water is devoid of any salts. Pure water can conduct electricity when a pinch of common salt is added to it as the salt solution is conducting in nature.

Question 7. In case of fire, before the firemen use the water hoses, they shut off the main electric supply for the area. Explain why they do this.
Answer: Water may conduct electricity. If the electrical supply for the area is not shut off and water is poured over electrical appliances, then electricity may pass through the water and harm the firemen. That is why, in case of a fire, the firemen shut off the main electrical supply for the area before they use the water hoses.

Question 8. A child staying in a coastal region tests the drinking water and also seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
Answer: Impure water is the conductor of electricity. Sea water contains more impurities than drinking water found in the coastal region. Therefore, seawater conducts more electricity than drinking water. That is why the compass needle deflects more in the case of seawater.

Question 9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy rain pour? Explain.
Answer: When it rains heavily, the rainwater dissolves many impurities from the atmosphere, which make it impure and very conductive of electricity. The air becomes humid with this water and becomes very conductive. That is why, it is not wise for an electrician to do electrical repair work when it rains heavily, because he may get dreadful shock or even gets an electric shock.

Question 10. Paheli had heard that rainwater is as good as distilled water. So, she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reason?
Answer: Rainwater is, of course, as good as distilled water but, when it passes through the atmosphere It dissolves a lot of dust dirt and impurities and becomes conducting. So, when Paheli used a tester, its compass showed deflection.

Question 11. Prepare a list of objects around you that are electroplated.
Answer: The objects which are electroplated are:
1. Taps of water connection.
2. Parts of the bicycle.
3. Body of cars, motorcycles and tractors.
4. Handles of the doors.

Question 12. The process is used for the purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
Answer: The thick rod of impure copper should be attached to the positive terminal of the battery. This is because the free copper of the solution will get deposited on the thin rod and the loss of copper from the solution will be restored from the thick rod to the positive terminal of the battery. Thus, copper from the thick rod could be extracted.

KSEEB Class 8 Science Solutions For Chemical Effects Of Electric Current 

Chemical Effects Of Electric Current Activities

Question 1. Join the free ends of the tester together for a moment. This completes the circuit of the tester and the bulb should glow. However, if the bulb does not glow, it means that the tester is not working. Can you think of the possible reasons? Is it possible that the connections are loose? Or, the bulb is fused? Or, your cells are used up? Check that all the connections are tight. If they are, then replace the bulb with another bulb. Now test if the tester is working or not. If it is still not working then replace the cells with fresh cells.
Answer: In this activity, if the bulb does not glow, it means that either the connections of the circuit are loose or the bulb is fused or cells are used up. If the tester is working, it can be used to test the materials, i.e., whether it is a conductor or non-conductor of electricity.

Question 2. Collect a few small plastics or rubber caps of discarded bottles and clean them. Pour one teaspoon of lemon juice or vinegar into one cap. Bring your tester over this cap and let the ends of the tester dip into lemon juice or vinegar Take care that the ends are not more than 1 cm apart but at the same time do not touch each other. Does the bulb of the tester glow? Does lemon juice or vinegar conduct electricity? How would you classify lemon juice or vinegar—a good conductor or a poor conductor?

Answer: In this activity the bulb glows which shows that lemon juice and vinegar both conduct electricity, hence they are good conductors of electricity.

Question 3. Take the tray from inside a discarded matchbox. Wrap an electric wire a few times around the tray. Place a small compass needle inside it. Now connect one free end of the wire to the terminal of a battery. Leave the other end free. Take another piece of wire and connect it to the other terminal of the battery Join the free ends of two wires momentarily. The compass needle should show deflection. Your tester with two free ends of the wire is ready. Now repeat using this tester. Do you find a deflection in the compass needle the moment you dip the free ends of the tester in lemon juice?

Answer: Take out the ends of the tester from the lemon Juice, dip them in water and then wipe them dry. Repeat the activity with other liquids such as tap water, vegetable oil, milk, and honey. (Remember to wash and wipe the ends of the tester after testing each liquid). In each case observe whether the magnetic needle shows deflection or not.

Thus, lemon juice, vinegar, tap water, milk, curd and water, and soda are good conductors of electricity while vegetable oil, honey, kerosene oil, and distilled water are poor conductors of electricity or insulators.

Question 4. Take about two teaspoonfuls of distilled water in a clean and dry plastic or rubber cap of a bottle. (You may obtain distilled water from your school science lab. You may also get distilled water from a medical store or a doctor or a nurse). Use the tester to test whether distilled water conducts electricity or not. What do you find? Does distilled water conduct electricity? Now dissolve a pinch of common salt in distilled water. Again test. What do you conclude this time?
Answer: If the tester is put in distilled water, the bulb of the tester does not glow. This shows that distilled water does not conduct electricity. But when salt is dissolved in distilled water and again tested, the bulb glows which shows that water containing salts conducts electricity. Thus water which is free of salts is poor conductor while water with salts is a good conductor of electricity.

Question 5. Take three clean plastic or rubber caps of bottles. Pour about two teaspoonfuls of distilled water into each of them. Add a few drops of lemon juice or dilute hydrochloric acid to distilled water in one cap. Now in the second cap containing distilled water, add a few drops of a base such as caustic soda or potassium iodide. Add a little sugar to the distilled water in the third cap and dissolve it. Test which solutions conduct electricity and which do not. What results do you obtain?
Answer: First and second cap with acid and base respectively, conducts electricity whereas the third cap having sugar dissolved in distilled water does not conduct electricity.

Question 6. Take out carbon rods carefully from two discarded cells. Clean their metal caps with sandpaper. Wrap copper wires around the metal caps of the carbon rods and join them to a battery. We call these two-rod electrodes. (Instead of carbon rods, you may take two iron nails about 6 cm long.) Pour a cupful of water into a glass/ plastic bowl. Add a teaspoonful of salt or a few drops of lemon juice to water to make it more conducting. Now immerse the electrodes in this solution. Make sure that the metal caps of the carbon rods are outside the water. Wait for 3-4 minutes. Observe the electrodes carefully. Do you notice any gas bubbles near the electrodes? Can we call the change taking place in the solution a chemical change?

Answer: On passing an electric current through the conducting solution of lemon juice and water, a chemical reaction takes place. Water is dissociated into its constituent gases, ie., hydrogen and oxygen. Oxygen bubbles are formed on the electrode connected to the positive terminal of the battery and hydrogen bubbles are formed on the other electrode. Changes in the colour of solutions may occur depending on what solution and electrodes are used. This process is known as the chemical effects of current.

Chemical Effects Of Electric Current Class 8 KSEEB Questions And Answers 

Question 7. We will need copper sulphate and two copper plates of size around 10 cm x 4 cm. Take 250 ml. of distilled water in a clean and dry beaker. Dissolve two teaspoonfuls of copper sulphate in it. Add a few drops of dilute sulphuric acid to the copper sulphate solution to make it more conducting. Clean copper plates with sandpaper. Now rinse them with water and dry them. Connect the copper plates to the terminals of a battery and immerse them in copper sulphate solution.

Allow the current to pass for about 15 minutes. Now remove the electrodes from the solution and look at them carefully. Do you find any difference in any one of them? Do you find a coating over it? What colour is the coating? Note down the terminal of the battery with which this electrode is connected.

Answer: After removing the electrodes from the solution, we find that copper metal gets deposited on the plate at the negative of the battery. It is concluded that when an electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate. The free copper gets deposited on the plate acting as a cathode. Gradually, a layer of copper builds up on the plate. This process is known as electroplating.

Chemical Effects Of Electric Current  Additional Questions

Question 1. What are good conductors?
Answer: The substances that conduct electricity through them are called good conductors.

Question 2. Give four examples of insulators.
Answer: Air, wood, rubber and plastic.

Question 3. Name two metal objects which have a coating of another metal.
Answer: Handlebars of bicycles, bathroom taps.

Question 4. Is air a bad or good conductor?
Answer: A bad conductor.

Question 5. Which metal is plated on handlebars of cycles and the rim of wheels?
Answer: Chromium

Question 6. What is the full form of LED?
Answer: Light Emitting Diode.

Question 7. Which part of an atom is responsible for the flow of current?
Answer: Electron

Question 8. Why do most liquids conduct electricity?
Answer: Due to the presence of ions in them, most liquids conduct electricity,

Question 9. An LED is a more efficient device than a bulb. Why?
Answer: LED is more efficient because it can glow even when a weak or lost current flows through it.

Question 10. Do lemon juice or vinegar conduct electricity?
Answer: Yes, they conduct electricity.

Question 11. How is the conductivity of liquids tested?
Answer: By using a tester.

Question 12. Why is tin electroplated on iron to make cans used for storing food?
Answer: Tin is less reactive than iron. The tin coating prevents food from coming in contact with iron and thus prevents it from getting spoiled or corroded.

Question 13. What effect of current does electroplating show?
Answer: Chemical effect

Question 14. Which effect of current causes the bulb to glow?
Answer: Heating effect

Question 15. Name the three effects of electric current.
Answer: Heating, magnetic and chemical effects.

Question 16. How can the magnetic effect of current be checked?
Answer: By using a magnetic compass.

Question 17. What is electroplating?
Answer: The deposition of a thin layer of metal over another metal by electrolysis is called electroplating.

Question 18. What happens when an electric current is passed through the copper sulphate solution?
Answer: When an electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate. The free copper gets drawn to the electrode connected to the negative terminal of the battery and gets deposited on it.

Explanation Of Chemical Effects Of Electric Current In KSEEB Science 

Question 19. On what factors thickness of the electroplated items depend?
Answer:
1. Thickness of electroplated items depends upon:
2. The strength of the current passing through the circuit.
3. The concentration of the metal in the solution.
4. The duration of the time the article has been in the solution.

Question 20. With the help of a suitable diagram, explain the electrolytic refining of copper.
Answer: To purify copper, a thin plate of pure copper and a thick rod of impure copper are used as electrodes in the acidified solution of CuSO_4. Pure copper is used as a cathode and impure copper is used as the anode. When an electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate. The free copper gets drawn to the electrode connected to the negative terminal of the battery and gets deposited on it. From the impure copper electrode, an equal amount of copper gets dissolved in the solution. Thus, the loss of copper from the solution is restored and the process continues. The impurities are left behind at the anode.

Chemical Effects Of Electric Current Multiple Choice Questions

Question 1. An electric current can produce
1. Heating effect only.
2. Chemical effect only.
3. Magnetic effect only.
4. Chemical, heating, and magnetic effects.
Answer: 4. Chemical, heating, and magnetic effects.

Explanation:
1. Electric current causes a chemical reaction when it passes through a conducting solution. This is a chemical effect of electric current.
2. When an electric current passes through the bulb. Its filament gets heated and the bulb starts glowing. This is the heating effect of electric current.
3. When an electric current is passed through a circuit it produces a magnetic field around it. This is the magnetic effect of electric current.

Question 2. Boojho and Paheli performed experiments taking similar bulbs and cells but two different solutions

They found that the bulb glows more brightly as compared to that You would conclude that
1. Higher current is flowing through the circuit
2. Higher current is flowing through the circuit
3. Equal current is flowing through both circuits.
4. The current flowing through the circuits in the two setups cannot be compared in this manner.

Answer: 1. Higher current is flowing through the circuit
Explanation: Higher current is flowing through the circuit

Question 3. Boojho’s uncle has set up an electroplating factory near his village. He should dispose of the waste from the factory
1. In the nearby river.
2. In the nearby pond.
3. In the nearby cornfield.
4. According to the disposal guidelines of the local authority.

Answer: 4. According to the disposal guidelines of the local authority.
Explanation: Waste disposal is a major concern in the electroplating industry as it causes water pollution and releases a hazardous chemicals into water bodies. Hence it should be disposed of according to the guidelines of the local authority.

Question 4. When an electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates
1. The chemical effect of current.
2. The heating effect of current.
3. The magnetic effect of current.
4. The lightning effect of current.

Answer: 1. The chemical effect of current
Explanation: Conducting a solution through electric current cause’s chemical reaction. This causes a change in colour and this is the chemical effect of electric current.

Question 5. Which one of the following solutions will not conduct electricity?
1. Lemon juice
2. Vinegar
3. Tap water
4. Vegetable oil

Answer: 4. Vegetable oil
Explanation: Vegetable oil does not contain ions hence it cannot conduct electricity.

KSEEB Class 8 Science Chapter 14 Important Questions 

Question 6. Which of the following metals is used in electroplating to make objects appear shining?
1. Iron
2. Copper
3. Chromium
4. Aluminium

Answer: 3. Chromium
Explanation: Chromium metal is used in electroplating to make objects appear shining because chromium has shining properties and is scratch resistant.

Question 7. Which of the following solutions will not make the bulb glow?
1. Sodium chlorides
2. Copper sulphate
3. Silver nitrate
4. Sugar solution in distilled water
Answer: 4. Sugar solution in diluted water
Explanation: The sugar solution is neither acidic nor basic and it cannot ionize to conduct electricity. Similarly, distilled water has no ions in it to conduct electricity. Hence the mixture of sugar solution and distilled water will not conduct electricity.

Question 8. Fill in the blanks
1. The object to be electroplated is taken as ______electrode.
2. One of the most common applications of the chemical effect of electric current is ________
3. Small amount of mineral salt present naturally in water makes it a ______ of electricity.
4. Electroplating of  _________is done on objects like water taps and cycle bells to give them a shiny appearance.

Answer:
1. Cathode
2. Electroplating
3. Conductor
4. Chromium

Question 9. Why is a layer of zinc coated over iron?
Answer: Tron readily reacts with atmospheric air to form rust. In order to prevent it from rusting zinc is coated over iron.

Question 10. Will the solution of sugar in distilled water conduct electricity?
Answer: No, the sugar solution is neither acidic nor basic and it cannot ionize to conduct electricity.

Question 11. Name the effect of current responsible for the glow of the bulb in an electric circuit.
Answer: Heating effect of electric current.

Question 12. Boojho made the circuit given and observed that the bulb did not glow. On Paheli’s suggestion, he added one more cell in the circuit. The bulb now glows. Explain.

Answer: On adding another cell current flows through bulb sufficiently to make it glow.

Question 13. Paheli set up an experiment using liquid A in the beaker She observed that the bulb glows. Then she replaced the liquid A by another liquid B. This time the bulb did not glow. Boojho suggested replacing the bulb by an LED. They observed that the LED glows. Explain.

Answer: The current flowing through liquid B may be weak to make the bulb glow whereas it was strong enough to make the LED glow.

Simplified Notes For KSEEB Class 8 Science Electric Current 

Question 14. Paheli wants to deposit silver on an iron spoon. She took a silver nitrate (AgNO3) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What material should the other electrode be made of?
Answer: The spoon should be connected to the negative terminal of the battery. The other electrode should be made of silver.

Question 15. Why is tin electroplated on iron to make cans used for storing food?
Answer: Tin is less reactive than iron. In order to prevent iron from reacting with food, tin is coated over iron for storing food.

Question 16. Which of these two circuits A or B shows the correct observation?
Answer:

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

KSEEB Solutions for Class 8 Science Chapter 16 Light Points To Remember

Light: The natural agent that stimulates sight and makes things visible. Light is reflected from all surfaces. It is a form of energy.
Objects that give out light on their own are called luminous objects.
Objects that do not give out light on their own are called non-luminous objects.

Reflection of Light: Bouncing back of light after striking a shiny or polished surface, in the same medium, is called reflection.
Types of Reflection:
1. Regular Reflection: When a beam of parallel light rays is incident on a smooth and plane surface, the reflected rays will also be parallel. This type of reflection is called Regular Reflection. The reflection from a plane mirror is an example of regular reflection.
2. Diffused or Irregular Reflection: When light is incident upon a rough or uneven surface, it is reflected in many directions due to the presence of irregularities on that surface.

If a reflected light ray is reflected again on being incident on another surface, it is termed multiple reflection. Multiple reflections are used in periscopes. Periscopes are used in submarines, war tanks, and by soldiers in bunkers to see objects that are not visible directly. In a kaleidoscope, beautiful patterns are formed due to multiple reflections.

Laws of reflection:
1. The angle of incidence is equal to the angle of reflection.
2. Incident ray reflected ray, and the normal drawn at the point of incidence to the reflecting surface, lie in the same plane.
3. Lateral inversion is the effect produced by a plane mirror in reversing images from left to right. For e.g. our left hand will appear as right and vice versa.

The image formed by a plane mirror is:
1. Of the same size as that of the object
2. Left-right inverted
3. Erect and virtual
4. Formed behind the mirror at the same distance as the distance the object in front of the mirror

Two mirrors inclined to each other give multiple images. Sunlight is called white light; consists of seven colors. The splitting of light into its constituent colors is known as dispersion. Visually challenged persons can read and write using the Braille system.

Parts of the Human Eye:
1. Cornea: Transparent bulge on the front surface of the eyeball which protects the eye and helps in the refraction of light.
2. Lris: Coloured diaphragm behind the cornea which controls the amount of Light entering the eye.
3. Pupil: Dark hole in the middle of the iris through which light enters the eye.
4. Eye lens: Transparent, crystalline structure behind pupil and iris.
5. Ciliary muscles: Hole in the eye lens in position and control the focal length of the eye lens.
6. Retina: The surface of the rear part of the eyeball where the light entering the eye is focused.
7. Rods and Cones: Rod cells respond to the brightness of light while cone cells respond to colours.
8. Blindspot It is the least sensitive point where no rods and cones are present.
9. The space between the cornea and the eye lens is filled with aqueous humor.
10. The space between the eye lens and the retina is filled with vitreous humor.

Class 8 Science KSEEB Light Chapter Notes 

Light NCERT Textbook Exercises

Question 1. Suppose you are in a dark room. Can you see objects in the ream? Can you see objects outside the room? Explain.
Answer: We cannot see objects in dark rooms. But we can see objects outside the room, in case there is a light outside the room. To see an object needs light which must reflect from the object to the eyes.

Question 2. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer:
Regular reflection
1. The reflected rays are parallel to incident rays.
2. It occurs when an incident ray falls on a smooth or polished surface.
Diffused reflection
1. The reflected rays are not parallel to incident rays.
2. It occurs when an incident falls on a rough surface. No, diffused reflection is not the failure of the laws of reflection.

Question 3. Mention against each following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
1. Polished wooden table
2. Chalk powder
3. Cardboard surface
4. Marble floor with water
5. Mirror
6. Piece of paper.
Answer:
1. Regular reflection will occur because of the polished surface.
2. Diffused reflection will take place because it is a rough surface.
3. Diffused reflection will take place because it is not a polished surface.
4. Diffused reflection will take place because marble and water will form a prism.
5. Regular reflection takes place because a plane mirror is a polished surface.
6. Diffused reflection due to rough surface.

Question 4. State the law of reflection.
Answer: The laws of reflection are
1. The angle of the incident is equal to the angle of reflection.
2. The ray of incidence, ray of reflection, and normal to-the-point incidence lie in the same plane.

Question 5. Describe an activity to show that the incident ray, the reflected ray, and the normal at the point of incidence lie in the same plane.
Answer:
Material required: a white sheet of paper, a drawing board, drawing pins, and a comb.
Procedure:
1. A white sheet of paper on a drawing board is fixed.
2. A strip of plane mirror is taken and placed in the path of the light ray.
3. The ray of light will be reflected.
4. Angle of incidence and angle of reflection on the sheet of paper is drawn,
5. The incident and reflected rays along the paper is observed. Now the sheet of paper is bent a little at the position of the reflected lay.
6. Keeping the incident ray and the normal in the plane of the drawing board, the reflected ray is tried to be seen now
Observation: The incidence ray, reflected ay, and normal lie in the same plane.

Question 6. Fill in the blanks in the following.
1. Person 1 min front of a plane mirror seems to be 2m away from this image.
2. If you touch your left ear with a right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with your left hand.
3. The size of the pupil becomes large when you see in dim light.
4. Night birds have less cones than rods in their eyes.

Question 7. The angle of incidence is equal to the angle of | Ans: Laser torch can harm or even damage the eye. So,reflection.
1. Always
2. Sometimes
3. Under special conditions
4. Never
Answer: 1. Always.

Question 8. The image formed by a plane mirror is
1. Virtual, behind the mirror and enlarged
2. Virtual, behind the mirror and of the same size as the object
3. Real at the surface of the mirror and enlarged
4. Real, behind the mirror, and of the same size as the object
Answer: 2. Virtual, behind the mirror and of the same size as the object.

Question 9. Describe the construction of a kaleidoscope.
Answer: A kaleidoscope is an optical instrument used to see a number of beautiful patterns. It is made up of a circular cardboard tube or tube of thick chart paper in which rectangular mirror strips are joined together to form a prism. At one end of the tube, touching these mirrors, a circular glass plate is fixed, Several small pieces of colored glass are placed upon it. This end is closed by a ground glass plate and beautiful patterns are seen through the other end of the kaleidoscope.

KSEEB Class 8 Science Solutions For Light 

Question 10. Draw a labeled sketch of the human eye.
Answer:

Question 11. Gurmit wanted to perform using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advice?
Answer: Laser torch can harm or even damage the eye. So her teacher advised her not to do so.

Question 12. Explain how you can take care of your eyes.
Answer: The following care should be taken to keep our eyes healthy:
1. We should not look at the sun or a powerful light source directly.
2. Too light too much light is bad for the eyes.
3. If advised, suitable spectacles should be used.
4. We should always read from a normal distance for distinct vision.
5. We should never rub our eyes if any small particle or dust goes into the eyes.
6. Food containing Vitamin A should be used.

Question 13. What is the angle of incidence of a ray if the reflected rays are at an angle of 90 degrees to the incident?
Answer: The angle of incidence is 45°

Question 14. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Answer: Infinite number of images of the candle will be formed if it is placed between two parallel plane mirrors.

Question 15. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° Draw the reflected ray from the second mirror.

Answer:

Question 16. Boojho stands at A just on the side of a plane mirror Can he see himself in the mirror? Also, can he see the image of objects situated at P, Q, and R?

Answer: No, Boojho can’t see himself in the mirror. He can see the image of the object at P and 0 but not of R.

Question 17.
1. Find out the position of the image of an object situated at A in the plane mirror
2. Can Paheli at B see this image?
3. Can Boojho at C see this image?
4. When Paheli moves from B to C. where does the image of A move?

Answer: It is shown in the following picture.

1. Yes, Paheli can see the image of A.
2. Yes, Boojho can see the image of A.
3. Image of the object at A will not move as an object is not moving.

Light Class 8 KSEEB Questions And Answers 

Light Activities

Question 1. Fix a white sheet of paper on a drawing board or a table. Take a comb and close all its openings except one in the middle. You can use a strip of black paper for this purpose. Hold the comb perpendicular to the sheet of paper. Throw light from a torch through the opening of the comb from one side With a slight adjustment of the torch and the comb you will see a ray of light along the paper on the other side of the comb. Keep the comb and the torch steady. Place a strip of the plane mirror in the path of the light ray What do you observe?

Answer: It is observed that after striking the mirror, the ray of light is reflected in another direction.

Question 2. Perform again. This time use a sheet of stiff paper or chart paper. Let the sheet project a little beyond the edge of the Table Cut the projecting portion of the sheet in the middle. Look at the reflected ray. Make sure that the reflected ray extends to the projected portion of the paper. Bend that part of the projected portion on which the reflected ray falls. Can you still see the reflected ray? Bring the paper back to its original position. Can you see the reflected ray again? What do you infer?

Answer: Yes, the reflected ray of light is seen on the sheet. It is concluded that the entire sheet fixed on the drawing board represents a plane. The incident reflected rays and the normal lie in the plane of the paper.

Question 3. A source of light 0 is placed in front of a plane mirror PQ. Two rays OA and OC are incident on it Can you find out the direction of the reflected rays? Draw normals to the surface of the mirror PQ, at points A and C. Then draw the reflected rays at points A and C. How would you draw these rays? Call the reflected rays AB and CD, respectively. Extend them further. Do they meet? Extend them backward. Do they meet now? If they meet, mark this point as I. For a viewer’s eye at E do the reflected rays appear to come from point ? Since the reflected rays do not actually meet at I, but only appear to do so, we say that a virtual image of the point O is formed at I. As you have learned already in Class VII, such an image cannot be obtained on a screen.

Answer: An image formed by a plane mirror cannot be obtained on a screen. Thus, the plane mirror forms a virtual image.

Question 4. Imagine that parallel rays are incident on an irregular surface Remember that the laws of reflection are valid at each point of the surface. Use these laws to construct reflected rays at various points. Are they parallel to one another? You will find that these rays are reflected in different directions.

Answer: It is observed that the reflected rays are not parallel to each other due to irregularities in the reflecting surface. This type of reflection is known as diffused or irregular reflection.

Question 5. Take two plane mirrors. Set them at right angles to each other with their edges touching To hinge them you can use adhesive tape. Place a coin in between the mirrors. How many images of the coin do you see?

Now hinge the mirrors using the adhesive tape at different angles, say 45°, 60°, 120°, 180°, etc. Place some object (say a candle) in between them. Note down the number of images of the object in each case. Finally, set the two mirrors parallel to each other. Find out how many images of candles placed between them are formed
Answer:
1. When two plane mirrors are joined at right angles, then three images are formed.
2. When two plane mirrors are joined at 45°, 7 images are formed.
3. When two plane mirrors are joined at 60°, 5 images are formed.
4. When two plane mirrors are joined at 120°,2 images are formed.
5. When two plane mirrors are joined at 180°,1 image is formed.
6. When the plane mirrors are parallel to each other, infinite images are formed.

Question 6. To make a kaleidoscope, get three rectangular mirror strips each about 15 cm long and 4 cm wide. Join them together to form a prism Fix them in a circular cardboard tube or tube of thick chart paper. Make sure that the tube is slightly longer than the mirror strips. Close one end of the tube with a cardboard disc having a hole in the center, To make the disc durable, paste a piece of the transparent plastic sheet under the cardboard disc. At the other end, touching the mirrors, fix a circular plane glass plate Place on this glass plate several small pieces of colored glass (broken pieces of colored bangles). Close this end of the tube with a ground glass plate. Allow enough space for the color pieces to move around.

Answer: A variety of patterns are observed in the tube. Kaleidoscope operates on the principle of multiple reflections.

Explanation Of Light In KSEEB Class 8 Science 

Question 7. Get a plane mirror of a suitable size. Place it in a bowl (Katori) Fill the bowl with water. Put this arrangement near a window in such a way that direct sunlight falls on the mirror. Adjust the position of the bowl so that the reflected light from the mirror falls on a wall. If the wall is not white, fix a sheet of white paper on it. The reflected light will be seen to have many close their right eye. Look at the round mark now and repeat the activity. Does the cross-colors. How can you explain this?

Answer: The mirror and water form a prism and breaks up the light into its colors. The splitting of light into its colors is known as the dispersion of light. A Rainbow is a natural phenomenon showing dispersion.

Question 8. Look into your friend’s eye. Observe the size of the pupil. Throw light on her eye with a torch. Observe the pupil now. Switch off the torch, and observe her pupil once again. Do you notice any change in the size of the pupil? In which case was the pupil larger? Why do you think it was so? In which case do you need to allow more light in the eye, when the light is dim or bright?
Answer: When the light from the torch falls on the pupil, its size becomes smaller to allow less amount of light to enter the retina. When light is switched off, the pupil enlarges to allow more light to enter the retina. Thus, the pupil controls the amount of light entering the eye.

Question 9. Make a round mark and a cross on a sheet of paper with the spot to the light of the cross. The distance between two marks may be 6- 8 cm. Hold the sheet of paper at an arm’s length from the eye. Close your left eye. Look continuously at the cross. Move the sheet slowly towards you, keeping your eye on the cross. What do you find? Does the round mark disappear at some point? Now close your right eye. Look at the round mark now and repeat the activity. Does the cross disappear?

Answer: Yes, the cross disappears. The disappearance of the cross or the round mark shows that there is a point on the retina which cannot send messages to the brain when light falls on it.

Question 10. Get a square piece of cardboard of size 6-8 cm. Make two holes Thread a string through the two holes. Draw/paste a cage on one side of the cardboard and a bird on the other side. Twist the string and make the card twirl rapidly. Do you see the bird in the cage?

Answer: Yes, we can see the bird in the cage. Thus, the impression of an image persists in the retina for about 1/16th of a second.

KSEEB Class 8 Science Chapter 16 Important Questions 

Light Additional Questions

Question 1. Define dispersion of light.
Answer: Splitting up white light into seven colors when it passes through a glass prism is known as the dispersion of light.

Question 2. Name the colors in the order they appear in the spectrum of light.
Answer: VIBGYOR — Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

Question 3. What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray?
Answer: The angle of incidence = 45°

Question 4. What are the two factors responsible for an object being seen?
Answer: To be seen as an object, the sense of vision and light are required.

Question 5. What are illuminated objects?
Answer: Objects which reflect the light falling on them and can be seen are known as illuminated objects

Question 6. What is white light?
Answer: Sunlight is a mixture of seven colors also known as white light.

Question 7. Give one example of natural dispersion.
Answer: Formation of the rainbow.

Question 8. Which kind of spherical mirrors are used in vehicles? Why?
Answer: A convex mirror is used in vehicles because it gives the driver a large field of view.

Question 9. Why is it important to take care of our eyes? Mention any two activities that may cause damage to our eyes.
Answer: Eyes are the most wonderful gift of nature to us and they must serve us for our whole life. Our eyes can be damaged by playing carelessly or by hurting them with sharp projections

Question 10. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Answer: The objects cannot be seen inside the room because there is no light. The objects outside the room can only be seen if there is light outside.

Question 11. Distinguish between real and virtual images.
Answer: Differences:
Real image
1. The rays actually meet at a point.
2. The image can be obtained on a screen.
Virtual image
1. The rays do not meet at a point.
2. The image cannot object obtained on a screen.

Question 12. What is color blindness? Give a reason for this defect.
Answer: Some people cannot distinguish between the different colors. This is known as color blindness. Colour blindness is due to the absence of cones on the nerve endings on the retina.

Question 13. What are cones and rods? What are their functions?
Answer:
1. Cones are nerve endings that are sensitive to color light. They help us to distinguish between colors.
2. Rods are nerve endings that are sensitive to bright light.

Question 14. How do visually impaired people communicate?
Answer: Visually impaired people can communicate by following methods
1. By using the Braille system which employs groups of dots to represent printed letters and numbers.
2. In 1980, Braille computer software was developed. It can input, output, and translate documents to and from Braille.
3. By speech technology that can convert ordinary text into speech.

Question 15. Give some uses of plane mirrors.
Answer: Plane mirrors are used for dressing up, shaving beards, in scientific meters, and far designing periscopes.

Detailed Notes On Light KSEEB 

Light Multiple Choice Questions

Question 1. Part of the eye which controls the light entering is called
1. Iris
2. Cornea
3. Lens
4. Retina
Answer: 1. Iris
Explanation: Iris is a dark muscular structure that exists behind the cornea. Its function is to control the entry of light.

Question 2. We can see a non-luminous object when light:
1. Emitted by the object falls on the eye.
2. Is reflected from the object towards our eye.
3. Completely passes through the object.
4. Gets completely absorbed by the object.
Answer: 2. Is reflected from the object towards our eye.

Question 3. Light falling on surfaces S1, S2, and S3 Surfaces on which the angle of incidence is equal to the angle of reflection is/are
1. S1 only
2. S1 and 82 only
3. S2and $3
4. All the three surfaces

Answer: 4. All the three surfaces
Explanation: Laws of reflection are always followed irrespective of the surface of the object hence the angle of incidence is equal to the angle of reflection.

Answer 4. A tiny mirror M is fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of the eye with respect to the position of the bulb as A, B, C, and D. In which position mirror will be visible?
1. A, 2. B, 3. C, 4. D

Answer: 1. A
Explanation: In the case of A ray of light from A strikes a mirror and gets reflected back to make an angle of incidence and angle of reflection equal.

Question 5. A small hole P is made in a piece of cardboard. The hole is illuminated bya torch The pencil of light coming out of the hole falls on a mirror. At which point should the eye be placed so that the hole can be seen?
1. A, 2. B 3. C 4. D

Answer: 1. A
Explanation: The eye should be placed at position A because the hole can be seen only when the angle of incidence is equal to the angle of reflection.

Question 6. Two mirrors A and B are placed at right angles to each other

A ray of light incident on mirror A at an angle of 25° falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be
1. 25° 2. 50° 3. 65° 4. 115°
Answer: 3. 65°
Explanation: The angle of reflection for the ray reflected from mirror B will be 65° because the reflected ray from mirror A forms an incident ray on mirror 6 and is then reflected back by an angle of 65°;

Question 7. Which of the following statements is correct regarding rods and cones in the human eye?
1. Cones are sensitive to dim light.
2. Cones are sensitive to bright light.
3. Rods are sensitive to bright light.
4. Rods can sense color.
Answer: 2. Cones are sensitive to bright light.
Explanation: Cones are sensitive to bright light hence they sense color whereas rods are sensitive to dim light and they cannot sense color.

Question 8. In the figure of the human eye, the cornea is represented by the letter
1. A 2. B 3. C

Answer: 3. C
Explanation:
1. Iris
2. Lens
3. Cornea

Simplified Notes For KSEEB Class 8 Science Light 

Question 9. Name the part of the eye which gives color to the eyes
Answer: Iris the part of the eye which gives color to the eyes.

Question 10. Book while waving his hand very fast in front of his eyes, observes that his fingers for it?
Answer: The persistence of vision is the reason for their blurred vision Boojho while waving his hand very fast in front of his eyes, observes that his fingers appear blurred.

Question 11. How many times is a ray of light reflected by two plane mirrors placed parallel and facing each other?
Answer: An infinite number of times a ray of light is reflected by two plane mirrors placed parallel and facing each other.

Question 12. the angle between the incident ray and the reflected ray is 60°. What is the value of the angle of incidence?
Answer: 30°.
Explanation: The angle of reflection is equal to the angle of incidence. Since the Angle of incident ray + Angle of reflected ray is 60°.
The angle of incidence = 30°

Question 13. The distance between the object and its image formed by a plane mirror appears to be 24 cm. What is the distance between the mirror and the object?
Answer: The distance will be 12 cm
Explanation: Object + image formed =24 cm
Object + mirror =12 cm

Question 14. What happens to light when it gets dispersed? Give an example.
Answer: When the light gets dispersed it is split into its constituent colors. Ex: rainbow.

Question 15. showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.

Answer:

Question 16. Can the image of the child in it be obtained on a screen?

Answer: No, the image of the child cannot be obtained on a screen because the image is a virtual image.

Question 17. Eyes of the nocturnal birds have large cornea and a large pupils. How does this structure help them?
Answer: They can see objects even in faint light. As a large pupil and large cornea allow more light to enter their eyes.

Question 18. What kind of lens is there in our eyes? Where does it form the image of an object?
Answer: Our eyes have a convex type of lens and the image is formed on the retina.

Question 19. Which part of the eye gets affected if someone is suffering from cataracts? How is it treated?
Answer: If a person is suffering from cataracts their eye lens will be cloudy. Cataracts can be treated by replacing the opaque lens with an artificial lens.

Question 20. Boojho planned an activity to observe object A through pipes so that he could see objects which he could not directly see.

1. How many mirrors should he use to see the objects?
2. Indicate the positions of the mirrors in the figure.
3. What must be the angle with respect to the incident light at which he should place the mirrors?
4. Indicate the direction of the rays
5. If any of the mirrors are removed, will he ee be able to see the objects?

Answer:
1. Three mirrors should he use to see the SHOU AN ee Pio Anat objects.

Question 21. There is a mistake in each of the following directly see. ray diagrams given
Answer:

Question 22. Explain the process which enables us to perceive motion in a cartoon film.
Answer: Carton movie is actually a projection of a static picture. 24 pictures per second are shown in a specific order which gives us the perception of movement.

Question 23. How is the phenomenon of reflection used in making a kaleidoscope? What are the applications of a kaleidoscope?
Answer: The kaleidoscope gives a number of images formed by reflection from the mirrors inclined to one another. Designers and artists use kaleidoscopes to get ideas for new patterns to design wallpapers, Jewellery, and fabrics.

Question 24. The word REST wrote in two ways in front of a mirror. Show how the word would appear in the mirror.
Answer:

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials: metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Conservation of Plants and Animals
• Chapter 7 Force and Pressure
• Chapter 8 Friction
• Chapter 9 Sound
• Chapter 10 Combustion and Flame
• Chapter 11 Cell Structure and Functions
• Chapter 12 Reproduction in Animals
• Chapter 13 Reaching the age of Adolescence
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water