NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev

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Class 9 : NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev

The document NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev is a part of the Class 9 Course NCERT Textbooks (Class 6 to Class 12).
All you need of Class 9 at this link: Class 9

Page No. 15
Ques.1. What is meant by a pure substance?
Ans: A pure substance is one which is made up of only one kind of particles either atoms or molecules. For example, oxygen, carbon, etc.

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Diamond: Pure substance
Ques.2. List the points of differences between homogeneous and heterogeneous mixtures.
Ans:

Homogeneous mixtures

Heterogeneous mixtures

1. The composition remains uniform throughout.

1. The composition does not remain uniform throughout.

2. The components of the mixture cannot be separated by visible boundaries.

2. The components of the mixture can be separated by visible boundaries.

3. Examples: A mixture of salt and water, ethanol and water.
3. Examples: A mixture of sand, sugar, chalk and water.


Page No. 18
Q.1. Differentiate between homogeneous and heterogeneous mixtures with examples.
Ans: 

Homogeneous Mixture
Heterogeneous Mixture
(i) Its composition is same throughout.
(i) Its composition is not same throughout.
(ii) It is transparent.
Examples: Copper sulphate solution and salt solution
(ii) It is opaque.
Examples: Muddy water, iron filings and sulphur powder


Ques.2. How are sol, solution and suspension different from each other?
Ans:

Sol

Solution

Suspension

They are
heterogeneous in nature.

They are
homogeneous in nature.

They are
heterogeneous in nature.

They scatter a beam of light and hence show Tyndall effect

They do not scatter a beam of light and hence do not show Tyndall effect

They do not scatter a beam of light and hence do not show Tyndall effect

They are quite stable.

Examples of solution are: salt in water, sugar in water.

Examples of suspension are: sand in water, dusty air


Q.3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Ans: Mass of solute (sodium chloride) = 36 g (Given)
 Mass of solvent (water) = 100 g (Given)
 Then, mass of solution = Mass of solute Mass of solvent
 = (36 100) g
 = 136 g

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev


Page No. 24
Q.1. 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?
Ans: Distillation is used to separate mixture of kerosene oil and petrol.

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev

1. Take mixture of petrol and kerosene in round bottom flask and set the apparatus as shown in the diagram.
2. Heat the flask till petrol changes into vapours.
3. Vapours of petrol will condense and petrol will be collected in a flask.
4. Now heat the mixture again so that kerosene oil changes into vapours.
5. Vapours of kerosene will get condensed and collect kerosene oil into another flask.

Q.2. Classify the following as chemical or physical changes:
• Cutting of trees
• Melting of butter in a pan
• Rusting of almirah
• Boiling of water to form steam
• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas
• Dissolving common salt in water
• Making a fruit salad with raw fruits
• Burning of paper and wood
Ans: 
• Cutting of trees → Physical change
• Melting of butter in a pan → Physical change

• Rusting of almirah → Chemical change
• Boiling of water to form steam → Physical change
• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change
• Dissolving common salt in water → Physical change
• Making a fruit salad with raw fruits → Physical change
• Burning of paper and wood → Chemical change 

Ques.3. Name the technique to separate
(i) butter from curd, (ii) salt from sea-water, (iii) camphor from salt.
Ans. (i) Centrifugation (ii) Evaporation (iii) Sublimation

Q.4. Try segregating the things around you as pure substances or mixtures.
Ans: 

MixtureSubstance
(a) Cold drink is a mixture.
 (a) Sugar is a pure substance.
(b) Milk is a mixture.
 (b) Distilled water is a pure substance.
(c) Brass is a mixture.
(c) Aluminium metal is a pure substance.
(d) Steel is a mixture.
(d) Alcohol is a pure substance.
(e) Tea is a mixture.
(e) Iodine is a Pure substance.


Q.5. What type of mixtures is separated by the technique of crystallization?
Ans: The crystallization method is used to purify solids.
1. Classify the following as chemical or physical changes:
 • Cutting of trees
 ► Physical change
 • Melting of butter in a pan

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Melting butter ► Physical change
 • Rusting of almirah
 ► Chemical change
 • Boiling of water to form steam
 ► Physical change
 • Passing of electric current through water, and water breaking down into hydrogen and oxygen gas
 ► Chemical change
 • Dissolving common salt in water
 ► Physical change
 • Making a fruit salad with raw fruits
 ► Physical change
 • Burning of paper and wood
 ► Chemical change

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Burning paper


Page No. 28
Ques.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) The 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) Wheat grains from husk.
(j) Fine mud particles floating in water.
Ans.  (a) Distillation
(b) Sublimation
(c) Filtration 
(d) Chromatography 
(e) Centrifugation
(f) Separating funnel
(g) Filtration 
(h) Magnetic separation
(i) Winnowing
(j) Filtration. 

Q.2. Write the steps you would use for making tea. Use the words: 
solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Ans: Take 100 ml of water which acts as solvent. Boil water with the help of gas stove. Now add one spoon of sugar which gets dissolved as it is soluble in water, acts as solute, and forms solution. Now add half a spoon of tea leaves which are insoluble in water. Let it boil for 2-3 minutes. Add half cup of milk and let it boil again for 3-4 minutes. Filter the tea with the help of sieve. Tea leaves will be left as residue whereas tea will be obtained as filtrate.


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



283293313333333
Potassium nitrate213262106167
Sodium chloride3636363737
Potassium chloride3535404654
Ammonium chloride2437415566

(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. What salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt?

Ans:  (a) At 313 K, 62 g of KNO3 is dissolved in 100 g of water. 31 g of salt will be dissolved in 50 g of water. 

(b) Crystals of KCI will be formed because when hot saturated solution is cooled. 
(c ) The solubility of KNO3 is 32 g, NaCl is 36 g, KCI is 35 g and NH4CI is 37 g per 100 g of water at 20°C, i.e. at 293 K. NH4CI has highest solubility. 
(d) The solubility of salts increases with increase in temperature.

Q.4. Explain the following giving examples:
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) Suspension

Ans: (a) Saturated solution: A solution in which no more solute can be dissolved at a particular temperature, is called saturated solution. 

(b) Pure substance: They have uniform composition and always have same properties like texture and taste, e.g. water, sodium chloride, sugar, oxygen.

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Sugar: pure substance(c) Colloid: The solution in which the particle size is between 1 nm, i.e. 10-9 m and 1,000 nm, i.e. 10-6 m, i.e. solute particles are 10 to 1,000 times bigger than the size of a single small molecule is called a colloid. The particles are smaller than those in suspension.
(d) Suspension: It is a heterogeneous mixture in which solid particles, which are insoluble in the solvent, remain suspended in the bulk of the medium and are visible to the naked eye.
Example: Muddy river water, chalk powder in water, sulphur powder in water, limestone particles in water, barium sulphate in water, dust storm.NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Paints
Ques.5. Classify each of the following as a homogeneous or heterogeneous mixture.
Soda water, wood, air, soil, vinegar, filtered tea.

Ans: Homogeneous mixtures: Soda water, air, vinegar.
Heterogeneous mixtures: Wood, soil, filtered tea.


Ques.6. How would you confirm that a colourless liquid given to you is pure water?
Ans: 
• Take given liquid in a boiling tube fitted with a cork.
• Suspend a thermometer into it so that it remains above water.
• Place boiling tube on a wire gauze and start heating with the help of burner.
• Note down the temperature at which water changes into vapours completely and the temperature of thermometer remains constant.
Observation: The given liquid boils at 100°C i.e., 373 K.
Conclusion: The given liquid is pure water because pure water boils at 100°C i.e., 373 K.


Ques.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: The following materials fall in the category of a "pure substance":
(a) Ice
(c) Iron
(d) Hydrochloric acid

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev

(e) Calcium oxide
(f) Mercury

Ques.8. Identify the solutions among the following mixtures:
(a) Soil
(b) Seawater
(c) Air
(d) Coal
(e) Soda water

Ans: The following mixtures are solutions:
(b) Seawater
(c) Air
(e) Soda water


Ques.9. Which of the following will show the "Tyndall effect"?
(a) Salt solution
(b) Milk
(c) Copper Sulphate solution
(d) Starch solution

Ans:  Milk and starch solution will show Tyndall effect because these are colloidal solutions in which path of light becomes clearly visible due to scattering of light.

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Tyndall effect
Ques.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: 

 NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRev

Ques.11. Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron fillings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of candle

Ans: The following changes are chemical changes:
(a) Growth of a plant
(b) Rusting of iron

NCERT Solutions, Is Matter Around Us Pure Class 9 Notes | EduRevFig: Rusting of iron(d) Cooking of food
(e) Digestion of food

(g) Burning of candle.

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