RBSE Class 9 Science Chapter 2 Is Matter around Us Pure Solutions

This post includes all intext and end exercise questions answer prepared by our experienced faculties. These solutions give you opportunity to secure good grades in exams.

These solutions are based on NCERT Class 9 Science book prescribed by Rajasthan Board of Secondary Education.      

So these RBSE Class 9 Science solutions are very useful for you.

 

Chapter 2 -  Is Matter around Us Pure 

 

Intext Questions

Answer of Questions on Page No. 15

Q.1 What is meant by a substance?

Answer  

A pure substance consists of only one type of particles.

 

Q.2 List the points of differences between homogeneous

and heterogeneous mixture.

 Answer  

Answer of Questions on Page No. 18

Q.1 Differentiate between homogeneous and heterogeneous mixtures with examples.

Answer

     

           

 

Q.2 How are sol, solution and suspension different from each other?

Answer

 

Q.3 To make a saturated solution, 36g of sodium chloride

is dissolved in 100g of water at 293K. Find its

concentration at the temperature.

Answer  

Given,

   Mass of solute (sodium chloride) =36 g

   Mass of solvent (water) = 100 g

        

Mass of solution = Mass of solute + mass of solvent

                           = 36 g + 100 g

                           = 136 g

 

       

Answer of Questions on Page No. 19

Q.1Classify the following as chemical or physical

changes:

 1. Cutting of trees.

 2. Melting of butter in a pan.

 3. Rusting of almirah.

 4. Boiling of water to form steam.

5. Passing of electric current, through water and the

water breaking down into hydrogen and oxygen gases.

6. Dissolving common salt in water.

7. Making a fruit salad with raw fruits, and

8. Burning of paper and wood.

Answer  

Physical change

1.  Cutting of trees.

2.  Melting of butter in a pan.

3.  Boiling of water to form steam.

4.  Dissolving common salt in water.

5.  Making a fruit salad with raw fruits.

     

 Chemical change

1.  Rusting of almirah.

2. Passing of electric current through water and the water breaking down  into hydrogen and oxygen gases

3.  Burning of paper and wood.

 

Q2.Try segregating the things around you as pure substances or mixtures: 

Answer 

Pure substances:

1.    Distilled water

2.    Bread

 3.    Diamond

 4.    Graphite

 5.    Sugar

 6.    Gold

Mixture:

1.    Ice-cream

2.    Steel

3.    Paper

4.    Talc

5.    Kerosene Oil

6.    Solder wire

7.    Curd

8.    Air

Answer of Questions End Exercises

Q.1 Which separation techniques will you apply for the

separation of the following?

      

(a)  Sodium chloride from its solution in water.

(b)Ammonium chloride from a mixture of sodium

chloride and ammonium chloride.

(c)  Small pieces of metal from in the engine oil of a car.

(d)  Different pigment from an extract of flower petals.

(e)  Butter from curd.

(f)   Oil from water.

(g)  Tea leaves from tea.

(h)  Iron pins from sand.

(i)   Wheat grains from husk.

(j)   Fine mud particles suspended in water.

Answer   

(a)  Evaporation

 (b)  Sublimation

(c)  Filtration

(d)  Chromatography

(e)  Centrifugation

 (f)   Separating funnel

 (g)  Filtration

 (h)  Magnetic Separation

 (i)   Sieving

 

Q.2 Write the steps you would use for making tea. Use

the words solution, solvent, solute, dissolve, soluble,

insoluble, filtrate and residue.

Answer 

First a cup of water is taken as a solvent in a saucer pan

and heat it.. During heating, milk and tea leaves are

added to the solvent as solutes. Now we get a solution.

Then, the solution is poured through a strainer. The

insoluble part of the solution remains on the strainer as

residue. Sugar is added to the filtrate, which dissolves in

the filtrate. The resulting solution is the required tea.

 

Q.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 substance dissolved in 100 grams of

water to form a saturated solution.

 

 

Substance dissolved		Temperature in K
	283	293	313	333	353
Potassium nitrate Sodium chloride Potassium chloride Ammonium chloride	21 36 35 24	32 36 35 37	62 36 40 41	106 37 46 55	167 37 54 66

 

(a)   What mass of potassium nitrate would be needed to

produce a saturated solution of potassium nitrate in 50

grams of water at 313 K.

(b)Pragya makes a saturated solution of potassium

chloride in water at 353 K and leaves the solution to cool

at room temperature. What would she observe as the

solution cools? Explain.

(c)   Find the solubility of each salt at 293 K. Which salt

has the highest solubility at this temperature?

(d) What is the effect of change of temperature on the

solubility of a salt?

Answer   

   

Q.4 Explain the following by giving examples:

 (a)  Saturated solution                

 (b)  pure substance   

 (c)  Colloid                  

(d)  suspension

Answer

(a)Saturated Solution: A saturated solution is a solution

in which the    maximum amount of solute has been

dissolved at a given temperature. The solution cannot

dissolve beyond that amount of solute at that

temperature. If more solute added will settle down at the

bottom of the container as a precipitate.

           

 Suppose 300g of a solvent can dissolve a maximum of

100g of a particular solute at 25⁰C. Then, the solution

obtained by dissolving 100g of that solute in 300g of that

solvent at 25⁰C is said to be a saturated solution at 25⁰C.

(b)Pure Substance: A pure substance is a substance

consisting of a single type of particle, i.e., all constituent

particles of the substance have the same chemical

properties. Example- gold, silver etc.

(c)  Colloid: A colloid is a heterogeneous mixture. The

size of the solutes in this mixture is so small that they

cannot be seen individually with naked eyes, and

seems to be distributed uniformly throughout the

mixture. The solute particles do not settle down when the

mixture is left undisturbed. This means that colloid is

quite stable. Colloids cannot be separated by the process

of filtration. They can be separated by centrifugation.

Colloids show the Tyndall effect. For example, milk,

butter, foam, fog, smoke, clouds.

(d)Suspension:Suspensions are heterogeneous mixtures.

The solute particles in this mixture remain suspended

throughout the medium. The particles can be seen with

naked eyes. It shows the Tyndall effect. The 

solute particles settle down when the mixture is left

undisturbed. It means suspensions are unstable.

Suspensions can be separated by the method of filtration.

For example, mixtures of chalk powder and water, wheat

flour and water. Example- chalk- water, paints etc.

 

Q.5 Classify each of the following as a homogeneous or

heterogeneous mixture : soda  water, wood, air, soil,

vinegar, filtered tea.

Answer  

Homogeneous mixture: Soda water, air, vinegar, filtered

tea.

     

Heterogeneous mixture: Wood, soil.Air is a

homogeneous mixture of different gases. If some dust or

other particles are present, then air becomes a

heterogeneous mixture.

 

Q.6 How would you confirm that a colourless liquid given to you is pure water?

Answer     

Every liquid has a specific boiling point. Pure water has a

boiling point of 100⁰C (373K) at 1 atmospheric pressure.

If the given colourless liquid boils at slightly above or

below 100⁰C, then the given liquid is not pure water. It

must boil at sharp l00⁰C, Thus by observing the boiling

point, and we can confirm whether a given colourless

liquid is pure water or not.

 

Q.7 Which of the following materials fall in the category

of a ‘pure substance’?

 (a)  Ice              

 (b)  Milk

 (c)  Iron                    

 (d)  Hydrochloric

 (e)  Calcium oxide  

 (f)   Mercury

 (g)  Brick            

  (h)  Wood

  (i)   Air

Answer 

  Pure substances –

(a)      Ice             

(b)  Iron

(c)  Hydrochloric acid   

(d)  Calcium oxide

(e)  Mercury

 

Q.8 Identify the solutions among the following mixtures:

  (a)  Soil                    

 (b)  Sea water

 (c)  Air          

 (d)  Coal

 (e)  Soda Water

Answer    

The following mixtures are solutions –

       (b)  Sea water           (c)  Air

       (e)  Soda water

 

Q.9 Which of the following will show ‘Tyndall effect’?

  (a)  Salt solution                   

 (b)  Milk

 (c)  Copper sulphate solution    

 (d)  Starch solution

Answer    

Milk and starch solution will show the ‘Tyndall effect’.

 

Q.10Classify the following into elements, compounds and mixtures:

 (a)Sodium         (b)  Soil

 (c)Sugar Solution    (d)  Silver

 (e)Calcium Carbonate    (f)   Tin

 (g)Silicon          (h)  Coal

 (i)Air                 (j)   Soap

 (k)Methane              (l)   Carbon Dioxide

 (m)Blood

Answer   

Elements-

(a)        Sodium      (b)Sliver

(c)Tin          d)Silicon

 Compounds

(e)      Calcium Carbonate

Mixture –

(b)  Soil     (c) Sugar Solution

(h) Coal     (i) Air

(j) Soap     (m) Blood

 

Q.11 Which of the following are chemical changes?

  (a) Growth of a plant      (b)        Rusting of iron

  (c) Mixing of iron filings and sand (d) Cooking of food

 (e) Digestion of food       (f)        Freezing of water

 (g) Burning of a candle

Answer    

The following changes are chemical changes:

(a)     Growth of a plant  (b)Rusting of iron

(c) Cooking of food     (d) Digestion of food

 (e) Burning of candle