NCERT Most Important question & Solutions for class-9 Chapter-2 Is Matter Around us Pure(Chemistry) | Class-9 Science | EduGrown

NCERT Most Important question & Solutions for class-9 Chapter-2 Is Matter Around us Pure (Chemistry)

The start of class 9 marks the beginning of the foundation for class 11 and class 12. It is very important study the basics in order to understand each and every chapter properly. In this page, we have provided all the important question for cbse class 9 that could be asked in the examination. Students also need to study the ncert solutions for class 9 in order to gain more knowledge and understanding the lessons. Questions and Answers are way to learn the new things in a proper way. NCERT textbooks downloads for class 9 in pdf are also available for the students if they need more help. By downloading these books, they can study from it. Our experts also prepared revision notes for class 9 so that students should see the details of each and every chapters. Class 9 important questions are the best to revise all the chapters in the best way.

1.Describe any three properties of colloid.

Answer

(i) It is a heterogenous mixture.
(ii) Size of particles is too small to be seen by naked eye.
(iii) They scatter light passing through them making its path visible.
(iv) They do not settle down when left undisturbed.
(v) They cannot be separated by the process of filtration.

2.State the principle of separating two immiscible liquids by separating funnel. Describe an activity with diagram to separate a mixture of water and kerosene oil.

Answer

Immiscible layers separate out in layers depending on their densities in the separating funnel.


Activity to separate kerosene oil from water using a separating funnel:

• Pour the mixture of kerosene oil and water in the separating funnel as shown in the figure.

3.Differentiate between a true solution and a colloid.

Answer

True solution	Colloid
A true solution is a homogeneous mixture of two or more substances.	A colloidal solution is a heterogeneous mixture of two substances.
The size of the particles is less than one nanometer.	The range of particle size is between one nanometer to 1000 nanometer.
It is always transparent.	It is translucent.
The particles cannot be seen even with microscope.	The particles of a colloidal solution can be seen with microscope.
It does not show Tyndall effect.	It shows Tyndall effect.

4.Distinguish between physical change and chemical change.

Answer

Physical change	Chemical change
In a physical change, only physical properties such as colour, physical state, density, volume etc. change, chemical properties remain unchanged.	In a chemical change, the chemical composition and chemical properties undergo a change.
No new substance is formed in a physical change.	A new substance is formed in a chemical change.
Very little or no energy in the form of heat, light or sound is usually absorbed or given out in physical change.	A chemical change is always accompanied by a absorption or evolution of energy.
A physical change is a temporary change.	A chemical change is a permanent change.
The original form of substance can be regained by simple physical methods.	Original substance cannot be obtained by simple physical methods.
A physical change is reversible.	A chemical change is irreversible.

5. ‘Sea water can be classified as homogeneous as well as heterogeneous mixture.’ Comment.

Answer

Sea water is a mixture of salts and water which cannot be separated except by evaporation. Therefore, sea water is considered homogeneous. Sea water also contains mud, decayed plant, etc., other than salts and water, so it is heterogeneous also.

6.Based on which factor a solution is said to be diluted, concentrated or saturated?
Answer
A solution is said to be diluted, concentrated or saturated on the basis of the amount of solute dissolved in the solution.

7.List the points of differences between homogeneous and heterogeneous mixtures.

Answer

Homogeneous mixtures	Heterogeneous mixtures
Homogeneous mixtures have uniform composition.	Heterogeneous mixtures have non uniform composition.
It has no visible boundaries of separation between its constituents.	It has visible boundaries of separation between its constituents.

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

Answer

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 scatter a beam of light and hence 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

9.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.

Answer

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

 

10.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

Kerosene and petrol are miscible liquids also the difference between their boiling point is more than 25 ºC so they can be separated by the method of distillation.

 

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

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