Is Matter Around us Pure?| NCERT Solutions| Class 9| School Help by Gunjan

NCERT Solutions of Chapter: Is Matter Around us Pure? NCERT Solutions along with worksheets and notes for Class 9.

Page 15

(1) What is meant by a substance?

Ans- Substances are those matters that have specific chemical composition and specific properties.

Eg: – Gold, table salt etc.

(2) List the points of differences between homogeneous and heterogeneous mixtures.

Ans– Differences between homogeneous and heterogeneous mixtures are given below –

SN	Homogeneous mixture	Heterogeneous mixture
1.	mixture has uniform composition of substances throughout	mixture has non – uniform composition of substances throughout
2.	Has uniform properties throughout	Do not have uniform properties throughout

Page 18

(1) Differences between homogeneous and heterogeneous mixture with examples.

Ans– Differences between homogeneous and heterogeneous mixtures are given below –

SN	Homogeneous mixture	Heterogeneous mixture
1.	mixture has uniform composition of substances throughout	mixture has non – uniform composition of substances throughout
2.	Has uniform properties throughout	Do not have uniform properties throughout
3.	Eg:- Water, vinegar etc.	Eg:- Iron fillings and water, soil etc.

(2) How are sol, solution and suspension different from each other?

Ans- Differences between sol, solution and suspension are given below –

SN	Sol	Solution	Suspension
1.	Heterogeneous mixture	Homogeneous mixture	Heterogeneous mixture
2.	Show tyndall effect	Cannot show tyndall effect	Show tyndall effect
3.	Solute dispersed in solvent	Solute dissolves in solvent	Solute suspended in solvent
4.	Can not separate by filtration	Can not separate y filtration	Can be filtered
5.	Eg:- Mud	Eg:- Solution of sugar and water	Eg:- chalk in water

(3) To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293K.Find its concentration at this temperature.

Ans-

Page 22

(1)Arrange the gases present in the air in increasing order of their boiling points.

Ans – The increasing order of boiling points of gasses are given below –

Nitrogen(- 196⁰C), Argon (-186⁰C), Oxygen(-183⁰C)

(2) Which gas forms the liquids first as the air is cooled?

Ans- The gas which has lowest boiling point will form liquid. Therefore, Nitrogen( -196⁰C) will form liquid first.

Page 24 A

(1) How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25⁰C), which are miscible with each other?

Ans- We will separate separate a mixture containing kerosene and petrol by distillation . Distillation is a method in which a mixture of miscible liquids that boil without decomposition and have sufficient difference in their boiling points separated in its components.

Eg:- Take the mixture of kerosene and petrol in a distillation flask. Fit a thermometer in the apparatus (shown in figure). Heat the mixture and check temperature from thermometer. After some time kerosene vaporises and condenses and collected from the condenser outlet. Petrol is left behind in the distillation flask.

(2) Name the technique to separate

(i) butter from curd,

(ii) salt from sea- water,

(iii) camphor from salt.

Ans-

S N	Separate	Technique
1.	butter from curd	Centrifugation
2.	salt from sea- water	Evaporation
3.	camphor from salt	Sublimation

(3) What type of mixtures are separated by the technique of crystallisation?

Ans- Crystallisation is a process in which pure solid separates from a solution in the form of its crystal.

Eg:- Impurities of salt from sea water can be remove by crystallization process.

Page 24 B

(1) Classify the following as chemical and physical changes:

(a) cutting of trees

(b) melting of butter in a pan

(c) rusting of almirah

(d) boiling of water to form steam

(e) passing of electric current, through water and the water breaking down into hydrogen and oxygen goes.

(f) dissolving common salt in water

(g) making a fruit salad with raw fruits , and

(h) burning of paper and wood.

Ans-

SN	Activities	Physical change	Chemical change
1.	cutting of trees	yes
2.	melting of butter in a pan	yes
3.	rusting of almirah		yes
4.	boiling of water to form steam	yes
5.	passing of electric current, through water and the water breaking down into hydrogen and oxygen goes.		yes
6.	dissolving common salt in water	yes
7.	making a fruit salad with raw fruits	yes
8.	burning of paper and wood.		yes

(2) Try segregating the things around you as pure substances or mixtures.

Ans- Pure substances – Air, water, iron, dal uncooked etc.

Mixtures – shakes, milk, cook food etc.

Exercises

(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 containing sodium chloride and ammonium chloride.

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

(d) Different pigments 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) What grains from husk.

(j) Fine mud particles suspended in water.

Ans-

SN	Mixture	Separation technique
a.	Sodium chloride from its solution in water	Evaporation
b.	Ammonium chloride from a mixture containing sodium chloride and ammonium chloride	Sublimation
c.	Small pieces of metal in the engine oil of a car	Filtration
d.	Different pigments from an extract of flower petals.	Chromatography
e.	Butter from curd	Centrifugation
f.	Oil from water	Separating funnel
g.	Tea leaves from tea	Filtration
h.	Iron pins from sand	By using magnets
i.	Wheat grains from husk	Winnowing
j.	Fine mud particles suspended in water.	Centrifugation

(2) Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Ans- Take some water in a pan. Put solute milk and sugar in solvent water. Solute sugar dissolves in solvent water. Put tea leaves in this mixture. Tea leaves are insoluble while sugar is soluble. After, boiling this mixture, filter this mixture. Residue will leave in sieve and tea filtrate from the sieve.

(3) Pragya tested the solubility of the 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).

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

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

Ans-

(b) Crystal of the potassium chloride will be obtained after cooling at room temperature.

(c) The solubility of each salt at 293 K are given below –

Potassium nitrate – 32

Sodium chloride – 36

Potassium chloride – 35

Ammonium chloride – 37

Ammonium chloride has the highest solubility at 293 k.

(d)The increase of the temperature will increase the solubility of the salt and decrease of the temperature will decrease the solubility of the salt.

(4) Explain the following giving example.

(a) saturated solution

(b) pure substances

(c) colloid

(d) suspension

Ans-

(a) A solution in which the maximum amount of the solute is dissolved in solvent at a particular temperature is known as saturated solution.

Eg:- If 100 g of salt dissolved in 200 g of water at certain temperature. The solution is said saturated if no amount of solute salt can be dissolved.

(b) When all the particles of the matter are of same chemical nature, is called pure substance or pure matter.

Eg:- Water , salt etc.

(c) A heterogeneous mixture of very small particles which cannot be seen by naked eyes but particles can scatter light beam easily, is called colloidal solution.

Eg:- Milk, jelly, smoke etc.

(d) A suspension is unstable (suspension settle down when left undisturbed). Therefore, they can be separated by the filtration. When particles of suspension settle down they can not scatter light.

Eg:- Mixture of chalk and water

(5) Classify each of the following as a homogeneous or heterogeneous mixture.

Soda water, wood, air, soil, vinegar, filtered tea.

Ans-

Mixture	Homogeneous Mixture	Heterogeneous Mixture
Soda water	Yes
Wood		Yes
air	Yes
soil		Yes
vinegar	Yes
Filtered tea	Yes

(6) How would you confirm that a colourless liquid given to you is pure water?

Ans- Pure water boils at 100⁰C and 1 atmospheric pressure. If given liquid boils at 100⁰c and 1 atmospheric pressure than given liquid is pure water.

(7) Which of the following materials fall in the category of a “pure substance”?

(a) Ice

(b) Milk

(c) Iron

(d) Hydrochloric acid

(e) Calcium oxide

(f) Mercury

(g) Brick

(h) Wood

(i) Air

Ans-

Material	Pure Substance
Ice	Yes
Milk	No
Iron	Yes
Hydrochloric acid	Yes
Calcium Oxide	Yes
Mercury	Yes
Brick	No
Wood	No
Air	No

(8) Identify the solutions among the following mixtures.

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water

Ans-

SN	Mixture	Tyndall effect
a.	Salt solution	No
b.	Milk	Yes
c.	Copper sulphate solution	No
d.	Starch solution	Yes

(10) Classify 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

Ans-

SN	Name	Elements	Compounds	Mixtures
a.	Sodium	Yes
b.	Soil			Yes
c.	Sugar solution			Yes
d.	Silver	Yes
e.	Calcium carbonate		Yes
f.	Tin	Yes
g.	Silicon	yes
h.	coal			Yes
i.	Air			Yes
j	soap			Yes
K	Methane		Yes
l.	Carbon dioxide		Yes
m.	Blood			Yes

(11) Which of the following are chemical changes?

(a) Growth of a plant

(b) Rusting of Iron

(c) Mixing of Iron fillings and stand

(d) Cooking of food

(e) Digestion of food

(f) Freezing of water

(g) Burning of a candle

Ans-

SN	Name	Chemical changes
a.	Growth of a plant	Yes
b.	Rusting of iron	Yes
c.	Mixing of Iron fillings and stand	No
d.	Cooking of food	Yes
e.	Digestion of food	Yes
f.	Freezing of water	No
g.	Burning of a candle	Yes