Activity 2.2 NCERT Class 9 Science Is Matter Around Us Pure

Activity 2.2 NCERT Class 9 Science Is Matter Around Us Pure

Brief procedure:

Activity 2.2 asks us to prepare the various homogenous, colloidal solution, suspension and observe the beam of the light.

A. Few crystals of copper sulphate.
B. One spatula full of copper sulphate.
C. Chalk powder or wheat flour.
D. Few drops of milk or ink.

Observation/finding: 

A beam of light passes from A and B.

The beam of light does not pass through solution C and D.

Activity 2.2 NCERT Class 9 science
A colloidal solution disperses the light.
Explanation:

A and B forms a homogenous solution. Particles of a homogenous mixture are small and do not reflect light. As a result,  a homogenous solution does not block the passage of the light or disperse light; and we see a clear beam of light.

A colloidal solution and a suspension have a larger particle size. They disperse light in all direction. If the concentration of solute particles is high, a light beam cannot pass through them.

Inference: A homogenous mixture does not block the beam of the light while a colloidal solution or suspension block the light.

Next: Experiment to demonstrate solubility increases with temperature, Activity 2.3.

See also: Experiment to demonstrate a homogenous mixture can have variable colour intensity, Activity 2.1.

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