Notes of Ch 2 Is Matter Around us Pure| Class 9th Science

Notes of Ch 2 Is Matter Around us Pure| Class 9th Science

Topics in the Chapter

• Introduction
• What is Mixture and its types
• What is a solution and its properties
• Concentration of a solution

4. The solute particles cannot be separated from the mixture by the process of filtration.

5. The solution is stable and solute particles do not settle down when left undisturbed

.

Concentration of a solution

(i) Saturated solution: When no more amount of solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

(ii) Unsaturated solution: When more amount of solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

(ii) Solubility: The amount of the solute present in the saturated solution at the given temperature is
called its solubility.

The concentration of a solution is the amount of solute present in a given amount (mass or volume) of solution. Also, the amount of solute dissolved in a given mass or volume of solvent is called concentration of solution.

Concentration of solution = Amount of solute/Amount of solvent or Amount of solute/Amount of solution
(Here, amount means mass or volume)

Two methods of finding concentration of solution:

(i) Mass by mass percentage of a solution = (Mass of solute/Mass of solution) ×100

(ii) Mass by volume percentage of a solution = (Mass of solute/Volume of solution) ×100

What is a suspension and its properties

A suspension is a heterogeneous mixture in which the the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Ex: Chalk in water, smoke in the air

Properties of Suspension :

1. It is a heterogeneous mixture.

2. Particles of a suspension are visible to the naked eye.

3. Size of the particles is greater than 100 nm.

4. It is unstable mixture. Solute settles down at the bottom over period of time.

5. If the solution is passed through filter paper, solute and solvent gets separated.

6. It scatters light when light is passed through the solution i.e. it shows Tyndall effect.


What is a colloidal solution and its properties

Colloid solution is heterogeneous mixture in which the size of particles lies between the true solutions and suspensions.

• Colloidal particles can easily scatter a beam of visible light. This phenomenon is called Tyndall effect.

Properties of colloidal solution:

1. The particles of colloid can’t be seen by naked eyes individually.

2. It is a heterogeneous mixture and thus solute and solvent can’t be separated by filter paper.

3. Size of particles is smaller than suspensions but greater than solutions (1 nm to 100 nm).

4. It is a stable mixture. Particles do not settle down at the bottom over a period of time.

5. They do not settle down when left undisturbed which means colloid is quite stable.

Different methods of separation are used to get individual components from mixture. Heterogeneous mixtures can be separated into their respective constituents by simple physical methods like handpicking, sieving, filtration etc.

Obtaining coloured components from blue/black ink

Process of evaporation is used to obtain coloured components from blue/black ink. The process of evaporation is used to separate a substance which is dissolved in water.

• It is based on the fact that liquid vaporises easily than the solid.

• Helps in separating volatile substances from non-volatile substances.

Obtaining coloured components from blue/black ink

Process of evaporation is used to obtain coloured components from blue/black ink. The process of evaporation is used to separate a substance which is dissolved in water.

• It is based on the fact that liquid vaporises easily than the solid.

• Helps in separating volatile substances from non-volatile substances.