Question

Cheese is an example of
(A) aerosol
(B) Foam
(C) Solid sol
(D) Gel

Answer 1

A colloid is a heterogeneous system in which one substance is dispersed as very fine particles in another substance called dispersion medium. The essential difference between a colloid and a solution is particle size. Due to more surface area Colloidal particles per unit mass because of their size less than suspensions.

Complete step by step solution:
Colloids are classified as:
(a) The dispersion medium and dispersed phase of physical state
(b) Interaction between the dispersed phase and the dispersion medium
(c) Various types of particles size of the dispersed phase
Let us check the classification based on the physical state of the dispersed phase and the dispersion medium.
There are many types of colloidal systems that exist on the basis of either dispersed phase or dispersed phase are liquids, solids, or gases.

S.No	Dispersed phase	Dispersion medium	Type of colloid	Examples
1	Solid	Solid	Solid sol	Some colored glasses and gemstones
2	Solid	Liquid	Sol	Paints, cell fluids
3	Solid	Gas	Aerosol	Smoke. Dust
4	Liquid	Liquid	Emulsion	Milk, hair cream
5	Liquid	Solid	Gel	Cheese, butter, jellies
6	Liquid	Gas	Aerosol	Fog, insecticide sprays. Mist
7	Gas	Solid	Solid sol	Foam rubber
8	Gas	Liquid	Foam	Whipped cream, soap lather

From the classification, S.no 5 is a type of colloid where the dispersion phase is liquid and the dispersion medium is solid which is known as a Gel.
Hence, cheese is an example of Gel.

The correct answer is option D.

Note: A gas mixed with other gas forms a homogeneous mixture. That is Dispersed phase and dispersion medium are gas is not a colloidal solution. All gases are completely miscible means that they are soluble with each other, which represents a type of true solution.