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KSEEB Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure Important Concepts

Elements, compounds and mixtures. Homogeneous and heterogeneous mixtures, colloids and suspensions.

Matter or Substance
Matter around us is of two types:
1. Pure substances
2. Mixtures

Pure substance
A material which contains only one kind of atoms or molecule.
Eg: Hydrogen, oxygen, chlorine etc.
Pure substances are uniform throughout because it consists of only one kind of particle.
Eg: Water, sodium chloride etc

Read and Learn More KSEEB Solutions for Class 9 Science 

Mixture
A mixture contains more than one element or compound in any ratio.
Eg: Salt solution

Types of mixtures
Mixtures are of two types:
1. Homogeneous mixture
2. Heterogeneous mixture
Homogeneous mixture has uniform composition.
Eg: Sugar in water, water in alcohol.
Heterogeneous mixture does not have uniform composition.
Eg: Oil and water, salt and sulphur

Elements
An element is defined as the simplest form of the basic form of a pure substance which can neither be broken into nor built up from simpler b. Colloidal solution
substances by any physical or chemical method.

Compounds
A pure substance made up of two or more elements chemically combined together in a fixed
proportion by mass.

Solution
Solutionis a homogenous mixture of two or more substances.

Solute
The component of solution which is present in small amounts is called solute. Eg: Salt is a solute in salt solution.

Solvent
The substance which is present in large amounts is called solvent. Eg: Water is a solvent in salt solution.

Aqueous solution
The solutions that are made in water.

Is Matter Around Us Pure KSEEB Class 9 Question Answers 

Concentrated solution
The concentration of solution can be specified by measuring amount of solute dissolved per litre of solution.

Saturated solution
A solution in which no more solute can be dissolved at a particular temperature.

Unsaturated solution
A solution which contains less amount of solute than required to make it saturated.

Supersaturated solution
It is a solution which contains more dissolved solute than the saturation concentration.

Types of solution
Based on the size of solute particles solution can be classified into:
1. True solution
2. Colloidal solution
3. Suspension

Dispersion medium
The medium in which colloidal particles are dispersed is called the dispersion medium.
Eg: Water is the dispersion medium in milk.

Tyndall effect
When a beam of light is passed through a colloidal solution placed in a dark place, its path becomes clearly visible. It is due to scattering of light by the colloidal particles.
Eg: When a beam of light is thrown on screen observed in theatres.

Brownian movement
Constant random motion of colloidal particles in a zigzag path is called Brownian movement.
Eg: Abeam of fight enters a room through a small hole, dust particles move in a zigzag manner.

Centrifuging and its applications
Centrifuging is a process in which denser particles are forced to settle at the bottom and the lighter stay at the top when rotated at high speed.

Applications:
1. It is used in Diagnostic Laboratories for blood and urine test.
2. Used in washing machines to squeeze out water from wet clothes.
3. Used in dailies to separate butter from cream.

Crystallization and its applications
Crystallization is a process in which hot saturated solution of a compound in suitable solvent is cooled so as to get crystals of a pure substance.

Applications:
1. Purification of salt that we get from sea water.
2. Separation of crystals of alum from impure samples like Potash alum, copper sulphate etc.

Chromatography and its application
Chromatography is a process of separation of those solutes which dissolve in the same solvent.

Applications:
1. It is used to separate colours of the dye.
2. To separate pigments from natural colours.
3. To separate drugs from blood.

Applications of separating funnel
1. It is used to separate immiscible liquids having differences in their densities.
2. In the extraction of iron from its ore.

Miscible liquids
The liquids which mix with each other are called miscible liquids.

Immiscible liquids=
The liquids which do not mix with each other are called immiscible liquids.

Physical change
Those changes in which only the physical properties of a substance change but no new substances are formed.
Eg: Breaking of glass tumbler, melting of wax.

Chemical change
Those changes in which new substances are formed.
Eg: Burning of magnesium ribbon, rusting of iron.

Metals, non-metals and metalloids
Metals: They are malleable and ductile, good conductors of heat and electricity.
Eg: Iron, copper, silver etc.

Non-metals: They are neither malleable nor ductile, non-conductors of heat and electricity.
Eg: Hydrogen, oxygen sulphur etc.

Metalloids: They have properties in between those of metals and non-metals.
Eg: Silicon, germanium, arsenic etc.

Is Matter Around Us Pure Exercises

Question 1. Which separation techniques will you apply for the separation of the following?

1. Sodium chloride from its solution in water.
Answer Evaporation or distillation

2. Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
ammonium chloride.
Answer Sublimation

3. Small pieces of metal in the engine oil of a car.
Answer Filtration

4. Different pigments from an extract of flower petals.
Answer Chromatography

Class 9 Science Chapter 2 KSEEB Textbook Solutions 

4. Butter from curd.
Answer Centrifugation

5. Oil from water.
Answer Separating funnel

6. Tea leaves from tea.
Answer Filtration

7. Iron pins from sand.
Answer Magnetic separation

8. Wheat grains from husk
Answer Sieving or winnowing

9. Fine mud particles suspended in water
Answer Adding alum

Question 2. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Answer Take some water in a kettle and boil it. To the hot water add some tea leaves and boil. Add some sugar and milk and boil again. Filter the mixture through a sieve.
Solution – Tea filtrate
Solvent – Water
Solute – Sugar and milk
Dissolve – Sugar
Soluble – Caffeine in tea powder
Insoluble – Tea leaves
Filtrate-Tea

Question  3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below. (Results are given in the following table, as grams of substances dissolved in 100 grams of water to form a saturated solution)

1. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313K?
Answer Mass of Potassium Nitrate in lOOg of water at 313K = 62 g.
Mass of Potassium Nitrate in 50 g of water in the saturated solution at 313Kis
622
313K x50g =31g
lOOgg

2. Pragya makes a saturated solution of
potassium chloride in water at 353K and leave the solution to cool at room temperature. What would she observe as the solution cools? Explain.
Answer When a saturated solution of Potassium Chloride at 353K is cooled, the solubility of Potassium Chloride in water decreases. Asa result the amount of potassium chloride which exceeds its solubility at lower temperatures separates out as crystals.

3. Find the solubility of each salt at 293K. Which salt has the highest solubility at this temperature?
Answer
Solubility of PotassiumNitrate = 32g
Sodium Chloride = 36g
Potassium Chloride = 35g
Ammonium Chloride -37g
Therefore Ammonium Chloride has highest solubility at the temperature.

KSEEB Solutions for Is Matter Around Us Pure Short Notes 

4. What is the effect of change of temperature on the solubility of a salt?
Answer The solubility of salt increases with temperature.

Question 4. Explain the following giving examples.
1. Saturated solution
Answer A solution in which no more solute can be dissolved at a particular temperature.
Eg: The stage where no more sugar will dissolve in water.

2. Pure substance
Answer A pure substance contains the particles of only one kind of matter.
Eg: Copper, hydrogen, oxygen.

3. Colloid
Answer They are heterogeneous mixtures of solute and solvent. In which particle size lies in between those of true solution and suspension.
Eg: Face cream, muddy water etc.

4. Suspension
Answer In a heterogeneous mixture the solute particles are visible to the naked eye.
Eg: Bleaching powder in water.

Question 5. Classify each of the following as a homogeneous or heterogeneous mixture. Wood, soda water, vinegar, soil, air, filtered tea
Answer
Homogeneous mixture: Sodawater, vinegar, filtered tea
Heterogeneous mixture: Wood, air & soil.

Question 6. How would you confirm that a colourless liquid given to you is pure water?
Answer If the boiling point and freezing point of the given liquid come out to be 100°C or 0°C respectively under 1 atmospheric pressure, we can confirm that the liquid is pure water.

Question 7. Which of the following materials fall in the category of a pure substance? Ice, milk, iron, hydrochloric acid, calcium oxide, mercury, brick, wood and air.
Answer Ice, iron, calcium oxide, hydrochloric acid and mercury are pure substances because they contain particles of only one kind of matter.

Question 8. Identify the solutions among the following mixtures. Soil, seawater, air, coal, soda water.
Answer Sea water and soda water are solutions.

Question 9. Which of the following will show “Tyndall Effect”? Soil solution, milk, copper sulphate solution, starch solution.
Answer Milk and starch show Tyndall Effect because the particles are big enough to scatter light.

Question 10. Classify the following into elements, compounds and mixtures. Sodium, soil, sugar solution, silver, calcium carbonate, tin, silicon, coal, air, soap, methane, carbon dioxide and blood.
Answer

Question 11. Which of the following are chemical changes?
1. Growth of a plant
Answer Chemical change

2. Rusting of iron
Answer Chemical change

3 . Mixing of iron filings and sand
Answer Physical change

4. Cooking of food
Answer Chemical change

5. Digestion of food
Answer Chemical change

6. Freezing of water
Answer Physical change

KSEEB Class 9 Science Chapter 2 Important Questions 

7. Burning of candle
Answer Chemical change

Is Matter Around Us Pure Textual Questions

Question 1. List the points of differences between homogeneous and heterogeneous mixtures.
Answer
Homogeneous mixture
It has uniform composition and properties throughout.
Eg: Sugar in water and alcohol.
Heterogeneous mixture
It has non-uniform composition and different parts having different properties.
Eg: Sand and salt, water in oil

Question 2. What is meant by a pure substance?
Answer A pure substance is a homogeneous material consisting of a single type of particle and definite set of properties.

Question 3. How are true solution, colloidal solution and suspension different from each other?

Answer

Question 4. To make a saturated solution, 36g of Sodium Chloride is dissolved in lOOg of water at 293K. Find its concentration at this temperature.
Answer Mass of sodium chloride = 3 6 g
Mass of water = lOOg Mass of sodium chloride + water = 100 + 36= 136g
Concentration of sodium chloride solution

Mass of solute
Mass of solution = 36     1000
136

=26.47%

Question 5. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C) which are miscible with each other?
Answer The technique of simple distillation or fractional distillation is used.

Question 6. Name the technique to separate:

1. Butter from curd
Answer Centrifugation

2. Salt from seawater
Answer Crystallization or evaporation

3. Camphor from Salt
Answer Sublimation

Question 7. What type of mixtures are separated by the technique of crystallization?
Answer Homogeneous mixtures of a pure solid in the form of its crystals from solution are separated by the technique of crystallization.

Question 8. Classify the following as chemical or physical changes.

1. Cutting of trees
Answer Physical change

2. Melting of butter in a pan
Answer Physical change

3. Rusting of almirah
Answer Chemical change

4. Boiling of water to form steam
Answer Physical change

5. Passing of electric current through water and the water breaking down into hydrogen and oxygen gases.
Answer Chemical change

KSEEB Solutions Chapter 2 pure substances And Mixtures Class 9 

6. Dissolving common salt in water
Answer Physical change

7. Burning of paper and wood
Answer Chemical change

Question 9. Try segregating the things around you as pure substances and mixtures.
Answer Pure substances: Water, sodium chloride, dry ice, sugar, pure metals.
Mixtures: Milk, soil, minerals, alloys, cool drinks.

Is Matter Around Us Pure Additional Questions

Question 1. Classify the following as sol, solution and suspension.

1. Milk of Magnesia
Answer Sol

2. Coloured gemstones
Answer Solid sol

3. Aerated drinks
Answer Solution

4. Emulsion paint
Answer Emulsion

Question 2. What is tincture in Iodine? Identify solute and solvent in tincture of Iodine.
Answer A solution of iodine in alcohol is known as tincture of Iodine.
Solute – Iodine
Solvent-Alcohol

Question 3. Can we separate alcohol dissolved in water by using a separate funnel?
Answer Both alcohol and water are miscible and hence cannot be separated by using a separating funnel.

Question 4. Give an example of aqueous and nonaqueous solution.
Answer Aqueous – Acetone water
Non-aqueous – Ether-Benzene

Question 5. A solution contains 60 g of common salt in 240 g of water. Calculate the concentration in terms of mass by mass percentage of solution.
Answer Mass of solution = Mass of solute + Mass of water.
= 60 + 2401| 300 g                   60
Mass by mass percentage = x 100 = 20

Question 6. Smoke and fog both are aerosols. In what way are they different?
answer the dispersion medium of both smoke and fog is air and hence they are called aerosols. They are different from each other in the dispersed phase. In smoke dispersed phase consists of fine particles of gas. While in case of fog it consists of particles of water.

Question 7. Differentiate between mixtures and compounds.
Answer

Question 8. Name the solute and the solvent for the following mixtures.

1. Tincture of Iodine
2. Soda water
3. Sugar solution

Answer.

1. Tincture of Iodine – Solute is iodine and solvent is alcohol.
2. Soda water – Solute is carbon dioxide and solvent is water.
3. Sugar solution – Solute is sugar and solvent is water.

Question 9. Common examples of colloids

Question 10. Write the differences between physical and chemical changes.

Answer

Question 11. Write the differences between physical properties of metals and non-metals.
Answer

Question 12. A solution contains 50g of common salt in 350g of water. Calculate the concentration of solution.

Answer Mass of common salt(solute) = 50g
Mass of water(solvent) – 350g Total mass of salt + water(solution) = 400g
Mass by mass percentage of solution =
Mass of Solute x 100
Mass of Solution 50 100 = 12.5%
400

Is Matter Around Us Pure KSEEB Class 9 Detailed Solutions 

Is Matter Around Us Pure High Order Thinking Questions

Question 1. Three Students A, B, and C prepared mixtures using chalk powder, common salt and milk respectively in water. Whose mixture:
1. Would not leave Residue on filter paper after filtration.
2. Would show Tyndall effect.
3. Would give clean or transparent solution.
4. Could be filtered by filter paper.

Answer.
1. Mixture of common salt and water.
2. Mixture of chalk powder with water and milk with water.
3. Mixture of common salt and water.
4. Mixture of chalk powder and water.

Question 2. Write your observations when the following process takes place.
1. Abeam of light is passed through a colloidal solution.
2. A saturated solution of potassium chloride prepared at 608°C is allowed to cool at room temperature.
 
Answer.
1. The path of a light becomes visible,
2. Potassium Chloride crystallizes out.

Question 3. Write the role of the following in water
purification.
1. Sedimentation tank
2. Loading tank
3. Chlorination tank

Answer
1. To allow solids to settle
2. To sediment the suspended impurities
3. To kill bacteria

Question 4. How is heating of sugar and heating of Ammonium Chloride different from each other?
Answer Ammonium chloride is a sublime, so it changes directly into gas on heating.
Sugar gets charred on heating to dryness.

Question 5. You are given two samples of water labelled as A and B. Sample A boils at 100°C and sample B boils at 102°C. Which sample of water will not freeze at 0°C? Comment.
Answer Sample B will not freeze at 0°C because it is not pure water. At 1 atm, the boiling point of pure water is 100°C and the freezing point of the pure water is 0°C.

Is Matter Around Us Pure Unit test Multiple choice questions

Question 1. Allows are______

1.  Pure substance
2.  Homogeneous mixtures
3. Compounds
4. Of fixed composition

Answer (2)

Question 2. Mixture o blue ink and red ink can be separated by_____

1. Evaporation
2. Separating funnel
3. Chromatography
4. Distillation

Answer (3)

Question 3. 1) Apure substance has fixed melting point
2) The properties of compound are similar to that of its components. Which is the correct statement______

1. Both A and B are true statements
2. A is true but B is false
3. A is false but b is true
4. Both A and B are false statements

Answer (2)

Question 4. The type of protein present in milk is______

1. Casein
2. Albumin
3. Soya bean
4. Keratin

Answer (1)

Is Matter Around Us Pure KSEEB Class 9 Question Answers 

Question 5. 24 karat gold is______

1. 100% pure gold
2. 99%GOLD
3. 95%Gold
4. 91%GOLD

Answer (1)

Is Matter Around Us Pure Fill in the blanks

1. Distilled water is a pure substance.
2. Air is a mixture.
3. The liquids which do not mix are immiscible liquids.
4. Iodised salt is a heterogeneous mixture of sodium chloride and potassium Iodine.
5. The process used by milkmen to separate cream from milk is centrifugation.
6. The concentration of poisonous gases in air is expressed in parts per million ppm.

Is Matter Around Us Pure Answer the following one mark

Question 1. Is rainwater or distilled water a pure substance?
Answer Yes, because it contains particles of only water.

Question 2. Give an example of non-aqueous solution.
Answer Iodine in carbon tetrachloride.

Question 3. The particle size of a substance A present in water is 200 nm. What is the nature of the solution?
Answer Suspension

Question 4. How will you separate the fine mud particles floating in water?
Answer By coagulation – Using alum and then filtering.

Question 5. What is Rust?
Answer When iron is exposed to air and moisture for a few days, a brown colour substance called rust is formed. Chemically rust is hydrated oxide of iron.

Is Matter Around Us Pure Answer the following Two Marks

1. What happens when a saturated solution is
1. Cooled
2. Further heated

Answer
1. When saturated solution is cooled some of the dissolved solid separates out because solubility usually decreases with temperature.
2. When a saturated solution is heated, it can dissolve more of the solute because solubility usually increases with temperature.

Question 2. Give one example of
1. A solid foam and solid Sol
2. Liquid in a liquid solution

Answer
1. Solid foam – Sponge, Rubber
2. Solid sol – Milky glass, coloured gemstone Liquid and liquid solution – Vinegar (acetic acid- water).

Is Matter Around Us Pure Activity

Question 1. 

Answer

Method/Experimental procedure
Put a few drops of blue or black ink on a watch glass and place it on a beaker ha full of water as shown in figure. The water in the beaker is heated and the steam thus formed will in turn heat up the ink.
Observation: The water present in the ink on a watch glass will evaporate and ultimately a blue or black Residue will be left on the watch glass.
Conclusion: This method can be used to separate non-volatile components (solutes ) dissolved in volatile solvents by the method of evaporation.

Question 2.

Answer

Method/Experimental procedure
Pour the mixture of kerosene oil and water in a separating funnel and keep undisturbed for some time so that separate layers of oil and water are fonned. Open the stop cock of the separating fimnel and pour out the lower layer of water carefully. Close the stop cock of the separating funnel as the oil reaches the stop cock.
Observation: Observe the setup carefully.
Conclusion: This technique is based on the principle that immiscible liquid separate out in layers depending on the densities.

Class 9 Science Chapter 2 KSEEB Textbook Solutions 

Question 3.

Answer

Method/Experimental procedure
The mixture of acetone and water in a distillation flask. Fit it with a thermometer. Arrange the apparatus as shown in figure. Heat the mixture slowly keeping a close watch at the thermometer.
Observation: The acetone vaporises and condenses in the condenser. Water is left behind in the distillation flask.
Conclusion: Thus, the separation of the liquid mixture into individual components can be achieved at their respective boiling points; the more volatile component distils over first, while the less volatile component distils over afterwards.
This technique is used to separate two miscible liquids by distillation.

Question  4. .

Answer

Method/Experimental procedure
A mixture consisting of Ammonium Chloride and common salt is taken in a China dish and is covered with a perforated filter paper. An inverted funnel is then placed on the China dish and its stem is closed with a cotton plug. The dish is heated gently.

Observation: The ammonium chloride changes into vapour, these vapours papers pass through the perforations of the filter paper and then get deposited on the inner surface of the funnel. The common salt remains in the China dish as Residue.
Conclusion: Thus, the process of sublimation can be used to separate sublimable volatile components from the non volatile components of a mixture.

Question  5. 

Answer

Method/Experimental procedure
Take a thin strip of filter paper. Draw a line on it using pencil, approximately 3 cm above the lower edge. Put a small drop of ink from a sketch pen or fountain pen at the centre of the line and let it dry. Suspend the paper in a glass jar containing water so that the spot of ink on the paper is just above the water level and leave it undisturbed.

Observation: As water rises up the paper by capillary action and flows over the spot, it takes along with it dye particles
Conclusion: The coloured component that is more soluble in water rises faster and in this way, the colours get separated.
This technique is used for separation of colours based upon the different solubilities in the same solvent

Question  6. Separation of two miscible liquids by fractional distillation.

Answer

Method/Experimental procedure
Take a mixture of two liquids chloroform and benzene in a distillation flask and boil the mixture. Set up the Apparatus as shown in figure and carry out experiment using a fractional column.
Observation: When the mixture is boiled, the vapours of less volatile liquid (benzene) condense more rapidly than the more volatile liquid (chloroform).
Conclusion: Vapours reach the top of the column and escape into the condenser, they consist entirely of the more volatile component i.e. chloroform will be collected in the flask.
Thus, separation of two miscible liquids whose is boiling points differ by less than 25 K can be achieved.

KSEEB Solutions For Class 9 Science Chapter 1 Matter In Our Surrounding Important Concepts

Types of matter, states of matter, characteristics, change of state – Melting, freezing, evaporation, condensation and sublimation.

Matter

• Matter is a substance which occupies space and has mass.
• Matter exists in three different physical states – solid, liquid and gas.
• Plasma is the fourth state of matter.
• The states of matter are interconvertible.

Change of state
The state of substance depends upon temperature and pressure.
Eg: Water exists as solid at 0°C, as liquid at room temperature whereas in gaseous state at 100°C.

Read and Learn More KSEEB Solutions for Class 9 Science 

Melting and melting p point
The process in which solid changes into liquid is called melting. The temperature at which solid changes into liquid completely is called melting point.

Boiling and boiling point
The process of converting liquid into vapour is called boiling. The temperature at which liquid changes into gas vapour is known as boiling point.

Sublimation
The process in which a solid state directly changes into gaseous state on heating or vice versa on cooling.

Condensation
The process in which a gas changes into liquid state by giving out heat at constant temperature.

Vaporization
It is a process in which liquid changes into vapour. It is a surface phenomenon.
It takes place at all temperatures.

Evaporation
It is a surface phenomenon. Particles from the surface present in the liquid and changes into the vapour state. Evaporation causes cooling.

Kelvin
Kelvin is the S.I. unit of temperature.
0°C = 273.16K (273K)
To change the Kelvin into Celsius scale subtract 273.16 from the temperature given in Kelvin. For converting 0°C to Kelvin (K) add 273.16.

Pascal
It is the S.I unit of pressure. 1 atm= l.OlxKfpa

Measurable quantities and their units

Matter In Our Surrounding Exercises

Question 1. Convert the following temperatures to the Celsius scale,
a. 293Kb. 470K

Answer
1. Temperature in the Celsius scale
= 293 – 273 = 20°C
293K = 20°C
2. Temperature in the Celsius scale = 493 – 273 m 197°C 470K = 197°C

Question  2. Convert the following temperatures to the Kelvin scale.
a. 25°C b. 373°C

Answer
1. Temperature in Kelvin = 25 + 273
— 298K = 25°C – 298K
2. Temperature in Kelvin – 373 + 273 = 646K
= 373°C = 646K

MatterIin Our Surroundings KSEEB Class 9 Question Answers 

Question  3. Give reasons for the following observations.
a. Naphthalene balls disappear with time without leaving any solid.
b. We can get the smell of perfume sitting several metres away.

Answer
1. By absorbing heat from the surroundings naphthalene balls slowly sublime, i.e solid naphthalene balls directly get converted into vapours and disappear with time without leaving any solid.
2. The molecules of perfume when entering in the air, diffuse in all directions as they are volatile and, therefore we can smell the perfume sitting several metres away.

Question  4. Arrange the following substances in increasing order of forces of attraction between the particles – water, sugar, oxygen.
Answer Oxygen, water and sugar.

Question  5. What is the physical state of water at___
a) 25°C b)0°C c) 100°C

Answer

1. In liquid state at 25°C.
2. In solid state at 0°C, when the heat is removed from it.
3. In gaseous state at 100°C when the heat is
supplied to it.

6. Give two reasons to justify____
a) water at room temperature is a liquid.
b) an iron almirah is a solid at room temperature.

Answer

a. 1. Intermolecular spaces are large.
2. Intermolecular forces are less and kinetic energy is more.
b. 1. Intermolecular forces are very large.
2. Intermolecular spaces and kinetic energy are very small.

Question  7. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer When the ice at 0°C (273K), there will be a change in phase, whereas in case of water at 0°C (273K) there will be no change in phase. Hence, lesser energy will be taken from the medium.

Question  8. What produces more severe burns, boiling water or steam?
Answer Steam produces more severe bums. Steam has the highest specific latent heat of vapourisation.

Question  9. Name A, B, C, D, E and F in the following diagram showing change in its state.

Answer

1. Solid changes into liquid state by process of melting.
2. Liquid state changes to gaseous state by the process o (Vaporization or boiling.
3. Gaseous state changes to liquid state by the process of condensation.
4. Liquid state changes into gaseous state by the process of freezing.
5. Solid changes into gaseous state by the process of sublimation.
6. Gas changes into solid by the process of sublimation.

Matter In Our Surrounding Textual Questions

Question 1. Which of the following are matter? (Chair, air, love, smell, hate, almonds, thought, cold, cool drink and smell of perfume).
Answer Matter – chair, air, smell, almonds, cool drink

Question 2. Give reasons for the following observation,
a. The smell of hot sizzling food reaches you several metres away but to get the smell from cold food you have to go close.
Answer The smell of hot sizzling food particles possesses large kinetic energy and diffuses in air rapidly and reaches several metres away, whereas the particles of cold food process less kinetic energy and are not able to reach several metres away.

Question 3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer The force of attraction between the particles is not strong. This is a property of liquid. These are spaces in between the particles of water.

Question 4. What are the characteristics of the particles of matter?

Answer

1. All matter (elements or compounds) consists of very small particles which can exist independently and are called molecules.
2. There are intermolecular spaces in between the particles of matter.
3. Particles move continuously and possess kinetic energy

Question 5. The mass per unit volume of a substance is called density (density – mass/volume). Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk cotton and iron.
Answer The order of increasing density is exhaust from air, chimneys, cotton, water honey, chalk and iron.

Class 9 Science Chapter 1 KSEEB Textbook Solutions 

Question 6. a. Tabulate the difference in characteristics of states of matter.
b. Comment upon the following. Rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

Question 7. Give reasons.
a. A gas fills completely the vessel in which it is kept.
Answer The particles of a gas are constantly moving in all directions and hence they completely fill the vessel in which they are kept.

b. A gas exerts pressure on the walls of the container.
Answer The particles of gas move in all directions with different speeds and the particles of the gas collide with one another and also against the walls of the container.

c. A wooden table should be called a solid.
Answer A wooden table has definite shape, fixed volume and is rigid.

d. We can easily move our hand in air but to do the same through a solid block of wood we need a Karate expert.
Answer We can move our hand easily in air because the force of attraction between the particles of a gas is very weak. The particles of solid are very closely packed the force of attraction is very strong. Hence we need Karate expert to break a wood.

Question 8. Liquids generally have lower density as compared to solids. But you must have observed that ice Boats on water. Find out why?
Answer The density of ice is lower than that of water and hence ice floats over water.

Question 9. Convert the following temperature to Celsius scale.
a. 300K b. 573K
Answer a. 300K = 300-273 = 27°C
b. 573K= 573-273 = 300°C

Question 10. What is the physical state of water at
a. 250°C b. 100°C
Answer a. The physical state of water at 250°C is gaseous state i.e steam.
b. The physical state of water at 100°C is liquid as well as gas.

Question 11. For any substance why does the temperature remain constant during the change of state?
Answer During the change of state, heat is absorbed but this heat gets used up in changing the state by overcoming the force of attraction between the particles, thus there is no change in temperature although heat is being absorbed constantly.

Question 12. Suggest a method to liquefy atmospheric gases.
Answer By cooling the gases under high pressure and lower temperature, the atmospheric gases can be liquefied.

Question 13. Why does a desert cooler cool better on a hot dry day?
Answer In a hot dry day temperature of the atmosphere is high and the humidity of air is low. Both these factors increase the rate of evaporation and thus enormous cooling is produced.

KSEEB Solutions for Matter In Our Surroundings Short Notes 

Question 14. How does the water kept in an earthen pot (matka) become cool during summer?
Answer An earthen pot has small pores in the walls. The water oozes out slowly as it comes out of the surface of earthen pot, it evaporates. Hence evaporation makes earthen pot become
cool during summer.

Question 15. Why does our palm feel cold can we put some acetone or petrol or perfume on it?
Answer Acetone or petrol or perfume has low boiling points. When these are put on the palm, they quickly evaporate.

Question 16. Why are we able to sip hot tea or milk faster from a saucer than a cup?
Answer The rate of evaporation is faster in saucer because of the surface area.

Question 17. What type of clothes should we wear in summer?
Answer In summer we sweat more, therefore to keep our body cool we must wear cotton clothes, since cotton clothes are good absorber of water.

Matter In Our Surrounding Additional questions

Question 1. Give examples in which matter is present in the plasma state.
Answer Fluorescent tube and neon sign bulbs.

Question 2. Which gas is called dry ice? Why?
Answer Solid carbon dioxide is called dry ice because solid carbon dioxide gets converted directly into gaseous state without coming into liquid state when is kept pressure is kept constant at 1 atmosphere.

Question 3. Convert -10°C Into Kelvin scale.
Answer -10°C = -10 + 273 = 263K.

Question 4. What is the difference between a gas and a vapour?
Answer Gas will be in the stable state. Eg: Oxygen, nitrogen. Vapour will be in the unstable state.
Eg: Water vapour.

Question 5. Which phenomenon occurs during the following changes?

1. Formation of clouds.
Answer a. Condensation

2. Drying of wet clothes.
Answer b. Evaporation

3. Size of naphthalene balls decreases.
Answer c. Sublimation

Question 6. Can solid diffuse into solid? Give example.
Answer Yes solid diffuses into solid.
Eg: Chalk gets diluted into board.

Matter In Our Surroundings KSEEB Class 9 Detailed Solutions 

Question 7. What is the fifth state of matter?
Answer Bose-Einstein condensate.

8. How interconversion of matter can be achieved?
Answer
1. By changing the temperature,
2. By changing the pressure.

Question 9. Why alcohol is more volatile than water?
Answer The boiling point of alcohol is 7 8°C which is lower than that of water 100°C, therefore alcohol is more volatile than water.

Question 10. What happens when a solid is heated?
Answer First solid changes into liquid and then to gaseous state.

Matter In Our Surrounding High-order thinking questions

Question 1. Out of dry and wet air which is heavier?
Answer Wet air is heavier than dry air because water vapours are heavier than air.

Question 2. Give reasons

1. A gas fills the vessel in which it is kept.
Answer a. The force of attraction between the particles of gas is very less and particles move freely in all directions.

2. A wet handkerchief is placed on forehead of a person suffering from fever.
Answer Evaporation cause cooling.

3. When sugar crystals dissolve in water, the level of water does not rise appreciably.
Answer c. Particles of sugar crystals occupy the space between the particles of water,

4. A wooden table should be called a solid.
Answer Wooden table has a fixed shape as well as fixed volume.

KSEEB Class 9 Science Chapter 1 Important Questions 

Question 3. Conversion of solid-state to liquid state is called fusion. What is meant by latent heat of fusion?
Answer The amount of heat required to convert 1 kg of solid to liquid at one atmospheric pressure at its melting point is known as latent heat of fusion.

Matter In Our Surrounding Unit Test Multiple Choice Questions

Question 1. Evaporation is called as _____

1. Surface phenomenon
2. Bulk phenomenon
3. pressure phenomenon
4. Unique phenomenon

Answer (1)

Question 2. When water gets solidified into ice, then heat is_____

1. Evolved
2. Absorbed
3. First absorbed then evolved
4. Initially evolved and then absorbed

Answer (1)

Question 3. Seetha visited an LPG unit and found that the gas can be liquefied at specified conditions of temperature and pressure. Help her to identify the correct set of conditions.____

1. High temperature and high pressure
2. Low temperature and low pressure
3. Low temperature and high pressure
4. High temperature and low pressure

Answer (3)

Matter In Our Surrounding Fill in the blank

1. The temperature at which solid changes into liquid is
called melting point
2. The physical state of Iodine is solid
3. ST unit of temperature is Kelvin

Matter In Our Surrounding Answer the following

1. Why oxygen is called gas?
Answer Oxygen has neither fixed shape nor fixed volume. Oxygen diffuses in air easily.

Question 2. Arrange honey, water and hydrogen in descending order on the basis of following properties exhibited by them.
a. Kinetic energy b. Density
Answer kinetic energy – Hydrogen > water > honey Density – Honey > water > hydrogen

Question 3. At what temperature vaporization takes place?
Answer At all temperatures.

Question 4. Why do we feel cool after applying shave lotion or perfume?
Answer Because shave lotion or perfume gets evaporated and causes cooling.

Question 5. The following triangle exhibits inter-conversion of three states of matter. Complete the triangle by labelling the arrows marked A, B, C and D. Liquid

Answer

1. Fusion
2. Vaporization
   
3. Condensation
4. Sublimation

Activity

Question 1. To demonstrate that particles of matter have space between them.

Answer Take a 100 ml beaker. Fill half the beaker with water and mark the level of water. Dissolve some salt with the help of a glass rod.
1`. Where does salt disappear?
Answer 1 . When we dissolve salt in water, the particles of salt get into the spaces between particles of water.

Question  2. To show that rate of intermixing increases the temperature.
Answer Drop a crystal of copper sulphate or potassium permanganate into a glass of hot water and another containing cold water. Do not stir the solution. Allow the crystals to settle at the bottom.

KSEEB Solutions Chapter 1 States Of Matter Class 9 

1. Does the rate of intermixing increase the temperature?
Answer Yes, with increase in temperature the kinetic energy of the particles increases. As a result, the rate of intermixing increases and hence the solid dissolves more quickly in hot water than in cold water.

Question 3. To demonstrate the process of sublimation.
AnswerTake some camphor or ammonium chloride, crush it and put it in a China dish. Put on inverted funnel over the China dish. Put a cotton plug on the stem of the funnel and heat slowly and observe.

1. What do you infer from the above activity?
Answer A change of state directly from solid to gas without changing into liquid state or vice versa is called sublimation.

KSEEB Solutions For Class 9 Science Chapter 4 Structure Of The Atom Important Concepts

Structure of an atom, electrons, protons and neu­trons. Atomic number and mass number, isotopes and isobars.

Atom
Atom is not the smallest indivisible particle but is made up of still smaller particles, i.e, electrons, protons and neutrons called fundamental particles are subatomic particles.

Proton
The fundamental particle which carries one nit positive charge and has mass nearly to that of hy­drogen atom.

Electron
The fundamental particle which carries one unit negative charge and has mass nearly to hydrogen atom.
\(=\frac{1}{1840} \text { th of } \mathrm{H} \text { atom }\)

Read and Learn More KSEEB Solutions for Class 9 Science 

Neutron
The fundamental particle which is neutral but has mass nearly equal to that of a proton.

Discovery of Subatomic particles
Electron -J. J Thomson Proton – Goldstein
Neutron – Chadwick

Atomic number(Z)
It is equal to the number of protons present in the nucleus.

Mass number(A)
It is equal to the sum of protons and neutrons.

Rutherford’s model of an atom

• An extremely small positively charged part at the centre called the nucleus in which the entire mass of an atom is concentrated.
• A number of negatively charged electrons surround­ ing the nucleus at relatively large distance from it. The number of electrons is equal to the net posi­tive charge on the nucleus.
• Nucleus and electrons are held together by the strong electrostatic forces of attraction.

Thomson’s model of an atom

• Inside the atom electrons are present.
• These electrons are embedded in spheres of posi­tive charge.
• Mass of an atom is due to electrons only.
• The negative and positive charges balance each
• Atom as a whole is neutral.

Bohr’s model of an atom

• An atom consists of a positively charged centre called the nucleus.
• Electrons revolve in orbits with well defined energy
• Electrons moving in the same orbit will not lose or gain energy.
• Supply of energy exits the electrons to high energy

Bohr-Bury Scheme

• First shell can have maximum 2, second shell can have maximum 8, third shell can have 18 elec­trons and 4th shell can have 32 electrons.
• Maximum number of electrons which can be ac­ commodated in an energy level of an atom is given by formula is 2n(n-The number of energy level)

Isotopes
Isotopes are the atoms of the same element pos­sessing different mass numbers but the same atomic number.
Example: Chlorine

₄₀Ar^{18     ₄₀K19}     

Isobars
The atoms of different elements, havingsome mass
number but different atomic numbers
Example: Argon, Potassium have same mass number but different atomic numbers.

Representation of atomic and mass number of an element.

A – Mass number
X – Symbol of the element
Z – Atomic number.
Example: 16 – Mass number   l¹10

O – Oxygen element
8 – Atomic number

Structure Of The Atom Exercises

1. Compare the properties of electrons protons and neutrons.

Answer:

2. What are the limitations of JJ Thomson’s model of the atom?
Answer: J. J. Thomson’s model could not explain the re¬ sults of the scattering experiment carried out by Rutherford.
3. What are the limitations of Rutherford’s model of the atom?
Answer:

1. Any charged particle when accelerated is ex¬ expected to radiate energy.
2. To remain in a circular orbit, the electron would need to undergo acceleration. Therefore, it would radiate energy.
3. The loss of energy would lead to shrinking of the size of the orbit. Inshort time it would hit the nucleus. Therefore an atom cannot be expected to be stable

Structure Of The Atom KSEEB Class 9 Question Answers 

4. Describe Bohr’s model of the atom.

Answer: Bohr put forward the following postulates about the model of an atom.

1. Only certain special orbits known as discrete orbits of electrons, are allowed inside the atom.
2. While revolving in discrete orbits the electrons do not radiate energy.

These orbits or cells are called levels and are rep­resented by the letters K, L, M, N

5. Compare all the proposed models of an atom given in the chapter.

Answer:
J. J. Thomson’s model of the atom
JJ Thomson recognized the subatomic par­ticles, i.e, electron and proton but failed to explain that how they are arranged within the atom and how they are shielded electrically.
Rutherford’s model of the atom
Rutherford’s model of the atom proposed that a very tiny nucleus is present inside the atom and electron revolve around the nucleus. The stability of that atom could not be explained by this model. Neil Bohr’s model of the atom

Neil bohr model of the atom
was more suc­cessful. He proposed that electrons are distrib­uted in different shells with discrete energy levels around the nucleus. If the atomic shells are com­plete, then the atom will be stable and less reac­tive.

6. Summarise the rules for writing of distribu­tion of electrons in various shells for the first 18 elements.

Answer: The number of electrons in different shells are fixed. The maximum number of electrons in any shell is given by the formula 2n² where n is the number of shell as counted from the nucleus.Maximum number of electrons in 1^st shell
(K shell) = 2n²= 2x 1²= 2
Maximum number of electrons in 2^nd shell
(L shell) = 2n²= 2*2²= 8
Maximum number of electro ns in 3^rd shell
(M shell) = 2n²=2×3²= 18
Maximum number of electrons in 4^th shell
(N shell) = 2n²=2×4²= 32

7. Define valency by taking examples of sili­con and oxygen.
Answer: Valency is defined as the number of electrons which an atom can lose or gain or share with other atoms so as to complete its octet. i.e, 8 electrons in the outermost shell.
Examples
1. Silicon
A tomic number of silicon =14
Number of electrons present =14
Electronic configuration= K – 2, L – 8, M – 4.
Thus, outermost shell has 4 electrons which it can share with other atoms to complete its orbit. Hence its valency = 4.

2. Oxygen
A tomic number of oxygen = 8
Number of electrons present = 8
Electronic configuration = K – 2, L – 6
Thus, outermost shell has 6 electrons. It will give two electrons to complete its octet. Hence valency = 2

8. Explain with examples

1. Atomic number
2. Mass number
3. Isotopes
4. Isobars

Structure Of The Atom Give any two uses of isotopes.

Answer:
1. Atomic number: The total number of protons present within the nucleus of an atom is known as atomic number.

Example: Sodium atom has 11 proton in its nucleus, therefore its atomic number is 11.

2. Mass number: The sum total of the masses of all the nucleons present in the nucleus of an atom, i e, number of protons and number of neutrons is called its mass number.

Example: Sodium atom has 11 protons and 12 neutrons in its nucleus, therefore its mass number is 11 + 2 = 23.

3. Isotopes: Atoms of the same element that have same atomic number but different mass numbers. Eg: Hydrogen has three isotopes.
\({ }_1^1 \mathrm{H} \quad{ }_1^2 \mathrm{H} \quad{ }_1^3 \mathrm{H}\)
The atomic number is 1 but mass numbers are 1,2,3.

4. Isobars: Atoms of different elements having same mass number but different atomic numbers. Eg: Calcium and Argon atoms have same mass number 40 but different atomic numbers 20 and 18.

₁₈Cl⁴⁰               _20^Ar40

9. Na+ has completely filled K and L shells. Ex­plain.

Answer: Atomic number ofNa =11, i.e, it has 11 elec­trons. According to Bohr – Bury scheme
1^st shel^; (n =1) i.e, K – Shell have maximum elec­trons = 2n² = 2x 1² = 2
2^nd shell (n =2) i.e, L – Shell have maximum elec­trons = 2n² = 2×2² = 8
The remaining one electron will enter into the 3^rd shell. Thus, K and L shells are completely filled.

Class 9 Science Chapter 4 KSEEB Textbook Solutions 

10. If bromine atom is available in the form of say two isotopes.

               35 Br ^{79   (49.7%)}                35 Br ^{81   (50.3%)}   

Calculate the average atomic mass of bro­mine atom.

Answer: The percentage of Br isotope with mass number
79 = 49.7
The percentage of Br isotope with mass number
81 = 50.3
Average atomic mass=\(\frac{49.7 \times 79 \times 50.3 \times 81}{100}\)
\(=\frac{3926.3+4074.3}{100}\)
= 39.263 +40.743 = 80.006 u

11. Average atomic mass of sample of an element X is 16.2u. What are the percentages of isotope 16/8x &18/8x in the sample?
Answer: The percentage of 16/8x be the “A”
Then the percentage of 18/8x will be = 100 – A
That means
\(\frac{\mathrm{A} \times 16+(100-\mathrm{A}) 18}{100}=16.2\)
16A+1800-18A=1620
-2A=-180
\(A=\frac{-180}{-2}=90\)
This suggests that, a percentage of 16/8x = 90
and therefore, percentage of
18/8x = 100-90= 10

12. If Z = 3, what would be the valency of the element? Also, name the element.
Answer: Element with Z = 3 is Lithium(Li)
Electronic configuration = \(\mathrm{K} \mathrm{L}
21\)
Thus, outermost shellhas 1 electron.
Hence, its valency = 1

13. Composition ofthe nuclei ofthe two atomic species X and Y are given as under:
\(\begin{array}{lll}
& X & Y \\
\text { Protons }= & 6 & 6 \\
\text { Neutrons }= & 6 & 8
\end{array}\)
Give the mass number of X and Y. What is the relationship between the two species?
Answer: Mass number = Number of protons + Number
of neutrons.
.’. Mass number ofX = 6 + 6=12
Mass number of Y = 6 + 8=14
As both contain the same number of protons i.e, 6, but they have different mass numbers i.e, 12 and 14. Hence, they are isotopes

14. Following statements, write T for true and F for false.
1. JJ Thomson proposed that the nucleus of an atom contains only nucleons. False
2. A neutron is formed by an electron and a proton combining together, therefore it is neutral. False
3. The mass of an electron is about 1/2000 times that of proton. True
4. An isotope of iodine is used for making tincture Iodine, which is used as medicine. False

15. Rutherford’s alpha-particle scattering ex¬ periment was responsible for the discovery of

1. Atomic nucleus
2. Electron
3. Proton
4. Netutron

Answer: 1. Atomic nucleus

16. Isotopes of an element have

1. The same physical properties
2. Different physical properties
3. Different number of neutrons
4. Different atomic numbers

Answer: 3. Different number of neutrons

17. Number of valence electrons in Cl ion are

1. 16
2. 8
3. 17
4. 18

Answer: 2. 8

18. Which of the following is a correct electronic configuration of sodium?

1. 2,8
2. 8, 2, 1
   
3. 2, 1, 8
   
4. 2, 8, 1

Answer: 2. 2, 8, 1

KSEEB Solutions For Structure Of The Atom Short Notes 

19. Complete the following table

Structure Of The Atom Textual Questions

1. What are canal rays?
Answer: The positively charged radiation produced in a discharge tube containing a gas at low pressure when a high potential difference is applied between the electrodes are called canal rays

2. If an atom contains one electron and one pro¬ ton will it carry any charge or not?
Answer: No, it will not carry any charge because electron carrier’s one unit negative charge whereas proton carries one unit positive charge. The net charge
on the atom will therefore be zero.
3. On the basis of Thomson’s model of an atom explain how the atom is neutral as a whole.
Answer:

Thomson’s Model of an atom.

According to Thomson’s model, the atom is considered as a sphere of positive charge in which negatively charged electrons are embedded like
seeds in a watermelon. The total negative charge on the electrons is equal to the total positive charge on the sphere. Hence, the atom as a whole is electrically neutral.

4. On the basis of rutherford’s model of an atom, which some subatomic particle is present in the nucleus of an atom?
Answer: Protons

5. Draw a sketch of Bohr’s model of an atom with three shells

6. What do you think would be the observation if the a-particle scattering experiment is carried out using a foil of a metal other than
gold?
Answer: With the foil of any heavy metal like gold, ex¬ ample: platinum, silver, etc, the observation will be same but with the fall of a light metal, example lithium, the massive a -particles may push the nucleus, and may not be deflected back.

7. Name the three subatomic particles of an atom.
Answer: Electron, proton, and neutron.

8. Helium atom has an atomic mass of 4u and
two protons in its nucleus. How many neu¬
trons does it have?
Answer: Mass number(atomic number) = 4
Number of protons = 2 i.e, Atomic number = 2
Number of neutrons = Mass number – Atomic
number = 4 -2 = 2

KSEEB Class 9 Science Chapter 4 Important Questions 

9. Write the distribution of electrons in carbon
and sodium atoms.
Answer: For carbon atoms, Atomic number ofC = 6
Number of electrons = Atomic number = 6
Electronic distribution= K/2 L/4
For sodium atom, Atomic number ofNa =11
Number of electrons =Atomic number = 11
Electronic distribution = K /2 L/8  M/1

10. If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
Answer: K-shell(n= 1) = 2 x 12 = 2
L shell (n = 2) = 2 * 22 = 8
When K and L shells are full, total number of electrons in the atom = 2 + 8 = 10

11. How will you find the valency of chlorine, sulphur, and magnesium?
Answer: Chlorine
Atomic number of chlorine =17
Electronic configuration = K, L, M
2 8 7
Valency of chlorine = 8-7=1 Sulphur
Atomic number of Sulphur = 16
Electronic configuration = K, L, M
2 8 6
Valency of sulphur =8-6 = 2
Magnesium
Atomic number of Magnesium = 12
Electronic configuration = K, L, M
2 8 2
Valency of magnesium is the number of valence electrons in the valence shell = 2.

12. If number of electrons in an atom is 8 and number of protons is also 8, then
1. What is the atomic number of the atom?
2. What is the charge of the atom?
Answer:
1. Atomic number = Number of protons = 8
2. As number of protons is equal to the number
of electrons, the atom will be neutral i.e, there is
no charge on the atom.

13. With the help of table find out the mass number of oxygen and sulphur atom.

Answer: Oxygen atom
Atomic number = 8
Number of protons = 8
Number of neutrons = 8
Number of oxygen = Number of protons + Number of neutrons
Sulphur atom
Number of protons = 1 6
Number of neutrons =16
Mass number of sulphur = Number of protons + Number of neutrons = 16 + 16 = 32u

14. For the symbol, H.D. and T tabulate three subatomic particles found in each of them.

15. Write the electronic configuration of any one pair of isotopes and isobars.
Answer: Isotopes of chlorine = \(\text { Isotopes of chlorine }=\begin{array}{cc}
35 & 37 \\
17 & { }_{17}^{3 l}
\end{array}\)
Electronic configuration of each of
= K L M 2
8 7 40
Isobars:\({ }_{18}^{40} \quad \text { Ar }_{20}^{40} \mathrm{Ca}\)
electronic configuration of Ar = K L M
2 8 8
Electronic configuration of Ca=K L M N
2 8 8 2

Structure Of The Atom Additional Questions 

1. Name the particles which determine the mass of an atom.
Answer: Proton and neutron

2. Write any two observations which support the fact that atoms are divisible.
Answer: Discovery of electrons and protons.

3. Why do Helium, Neon and Argon have a zero valency?
Answer: Helium has 2 electrons in its only energy shell, while argon and neon have 8 electrons in the valence shells. As these have maximum number of electrons in the valence shells, theydo not have any tendency to combine with other elements. Hence, they have a valency equal to zero.

Atomic Models Explained Class 9 KSEEB Solutions 

4. Find out the valency of element X having atomic number 16.
Answer: For element X
Atomic number = 16
Electronic configuration =2, 8, 6
Valency=8-6 = 2

5. List applications ofany three isotopes in various fields.
Answer:
1. An isotope of Uranium is used as a fuel in nuclear reactors.
2. An isotope ofCobalt is used inthe treatment of cancer.
3. An isotope ofiodine is used in the treatment of goiter

6. What do you mean by excited state of an atom?
Answer: When the electron in the atom absorbs energy and jumps to some higher orbit it is called excited state

8. Give examples from everyday life where we use cathode ray tubes.
Answer:
1. Television picture tube
2. Fluorescent light tubes or bulbs

9. What do you mean by
1. Valence electrons
2. Valence shell
Answer:
1. Valence electrons: The electrons present in the outermost shell ofan atom.
2. Valence shell: The outermost shellofan atom

10. What are nucleons?
Answer: Protons and neutrons present in the nucleus are
collectively called nucleons

1. Calculate the total number of electrons present in 1 mole of Methane.
Answer: Atomic number of C = 6. Thus, it has 6 electrons. Atomic number of H = 1. Thus, each H atom has one electron.
Number of electrons present in 1 molecule of
\(\mathrm{CH}_4\) = 6 + 4 = 10
Number of molecules in 1 mole of \(\mathrm{CH}_4\)
= 6.022 x \(10^{23}\)
Hence, 1 mole of will contain electrons
= 10×6.022 x \(10^{23}\)= 6.022 x \(10^{24}\)

2. Why did Rutherford choose gold and not another light element for his experiment?
Answer: Rutherford use gold for his experiment because he wanted as thin layer as possible for the experiment and gold foil was only about 1000 atom thick

3. Why atomic number is considered as better fundamental attribute of an element? State the reason.
Answer: Because elements are defined by the number of protons they possess. Chemical properties of an element change with the change in atomic num­ber.

4. An ion Z²⁺ contains 18 electrons and 20 neu­trons. Calculate the atomic number and mass number of element Z. Name the element Z.
Answer: Number of electrons in Z²⁺ ion = 18
Since positive ion is formed by the loss of elec­trons from the neutral atom and the number of electrons lost is equal to the number of units of positive charge on the ion.
Number of electrons in the neutral atom
= 18 + 2 = 20
Now, for a neutral atom,
Atomic number = Number of protons = Number of electrons
Thus, make number of element Z = 20
Mass number of element Z = Number of protons
+ Number of neutrons = 20 + 20 = 40
The given element Z with atomic number 20 is Calcium.

KSEEB Chapter 4 Class 9 Detailed Atomic Structure Solutions 

5. A student state that in an atom, the number of protons is greater than the number of neu­trons, which in turn is greater than the num­ber of electrons. Do you agree with this state­ment? Justify your answer.
Answer: No, statement is incorrect. In an atom the num­ber of protons and electrons is always equal.

6. How can you justify that protons are constitu­ents of all atoms?
Answer: The mass and charge of the nucleus of the atom of any element are found to be whole number mul­tiple of the mass and charge of proton. This shows that protons are present in all the atoms.

7. Give one application where electron beam is used.
Answer: Cathode rays (beam of electrons) when focused on a heavy metal like tungsten, molybdenum, etc, produce X – rays which find a wide application in medical field.

Structure Of The Atom Unit Test Multiple Choice Questions

1. Rutherford’s Alpha particle scattering experi­ment resulted into discovery of_______

1. Electron
2. Proton
3. Nucleus in the atom
4. Atomic mass
Answer: (3)

2. Elements with valency 1 are______

1. Always metals
2. Always metalloids
3. Either metals or nonmetals
4. Always nonmetals
Answer:(3)

3. Which of the following are true for an element?_______
a. Atomic number = number of protons + number ofneutrons
b. Mass number = number of protons + number of neutrons
c. Atomic mass = number of protons = number of neutrons
d. Mach number = number of protons = number of electrons

1. 1&2
2. 1&3
3. 2&3
4. 2&4

Answer: (4)

Structure Of The Atom Fill in the blanks

1 . Helium has 2 Valence Electrons and its valency is zero.
2. The heaviest particle in an atom is Neutron
3. The mass number is equal to number of neutrons 
4. 2nd energy level can have maximum 8 electrons.

Structure Of The Atom State true or false

1. Cathode rays travel in straight line. True
2. Neutrons does not have any charge. True
3. Cathode rays are positively charged. False

Structure Of The Atom Answer the following

1. What is the mass of an electron?
Answer:  \(\frac{1}{1836}\)of1 atomofH = 9.1x 10³¹kg 1836

2. Which isotope is used to detect blood clots?
Answer: Na – 24

3. Which of the following electronic configurations are not possible? Give reasons.

1. 2, 8, 4
2. 3, 8, 2
3. 2, 8, 9

Answer: 2. 3, 8, 2  3. 2, 8, 9
Because according to Bohr Buryscheme, the first shell can have maximum2 and the outermost shell can have a maximumof8 electrons only

4. Why are anode rays called canal rays?
Answer: The anode rays produced at the anode of the discharge tube are called canal rays because they pass through the holes ofthe cathode.

5. What observation scattering experiment prove that the most of the space in the atom is empty?
Answer: most of the Alpha particles pass through the thin foil of gold without undergoing any deflection.

6. Represent the three isotopes of Hydrogen.
Answer: Protium, Deuterium Tritium

7. What are cations and anions?
Answer: The positively charged species are called cations.
Example Na+
The negatively charged species are called anions.
Example: Cl

Structure Of The Atom Class 9 KSEEB Solutions 

8. Write the elec tronic configuration of
1. K – (19)
2. Ca – (20)
Answer:
K = 2, 8, 8, 1
Ca = 2, 8, 8,2

9. What is electronic configuration?
Answer: The distribution of electrons in various energy levels is called electronic configuration.

Answer the following

1. Compare any three important characteristics of isotopes with those of isobars.
2. What information do you get from the given figure about the atomic number, mass number and valency of atoms X,Y, and Z? Give your answer in a tabular form

3. List the differences between electron, proton, and neutron

4. List the properties of cathode rays.
Answer:
1. Cathode rays travel in straight lines.
2. Cathode rays are made up of material particles.
3. Cathode rays produce heating effect.
4. Cathode rays carry negative charge.
5. Cathode rays produce X-rays when they strike against the surface of hard metals like tungsten.

5. List the properties of anode rays.
Answer:
1. Anode rays travel in straight lines.
2. Anode rays are made up of material particles.
3. Anode rays carry positive charge.
4. Mass of the positively charged particles constituting the anode rays also depend upon the nature of the gas.

1. Rutherford’s model of an atom
Answer:

Experiment
Scattering of alpha particles by gold foil.
Observations
1. Most of the Alpha particles passed straight through the gold foil.
2. Some of the Alpha particles were deflected by the foil by small angles.
3. One out of every 12000 particles appeared to rebound.

Conclusions
1. Most of the space inside the atom is empty.
2. The positive charge of the atom occupies very little space.

Rutherford’s nuclear model of an atom
1. There is positively charged center in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus.
2. The electrons revolve around the nucleus in well-defined orbits.
3. The size of the nucleus is very small as compared to the size of the atom

2. Schematic atomic structure of the first18 elements