Question

Smoke is an example of:
(A) Solid dispersed in solid
(B) Solid dispersed in gas
(C) Solid dispersed in liquid
(D) Gas dispersed in solid

Answer 1

Hint: Smoke is a colloid. A colloid has a dispersed phase and a dispersion medium. The physical state of dispersed phase and dispersion medium gives us different types of colloids.

Complete step by step solution:
First we will define dispersed phase and dispersion medium.
> Dispersed phase is the colloidal particles present in the dispersion medium. They have relatively larger size than particles of true solution but smaller than the particles of suspension.
> Dispersion medium is the medium in which the colloidal particles are present. It can be a solid, liquid or gas.
> Now, let’s analyze the given options.
- In option (A), the solid is dispersed in solid. This is an example of solid sol. In this case both the dispersion medium and dispersion phase are solids. Coloured gems, pearls, etc. are some examples of solid sol.
- In option (C), the solid is dispersed in liquid. This is an example of sol. In this case the dispersed phase is solid while the dispersion medium is liquid. Paints, starch solution, etc. are some examples.
- In option (D), gas is dispersed in solid. This is an example of solid foam. In this case the dispersed phase is gas while the dispersion medium is a solid. Foam, rubber, etc. are few examples.
- In option (B), solid is dispersed in gas. This is an example of solid aerosol. In this case the dispersed phase is solid while the dispersion medium is a gas.
Smoke consists of solid dust particles suspended in air. So, it is an example of solid aerosol.
Hence, the answer to the given question is option (B).

Note: Students can get confused in solid dispersed in gas and gas dispersed in solid. Both are different as the dispersion medium and dispersed phase are different. So, their properties will also be different. In smoke the dispersed phase is solid while the dispersion medium is gas.