Question

How are colloids classified on the basis of:
(i) Physical states of components
(ii) Nature of dispersed phase
(iii) interaction between the dispersed phase and the dispersion medium

Answer 1

Hint: A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium. The essential difference between a solution and a colloid is that of particle size. Colloidal particles have an enormous surface area per unit mass as a result of their small size.

Complete step by step solution:
Colloids are classified based on the following criteria:
(i) Physical states of components: this classification is based on the physical state of the dispersed phase and dispersion medium. Depending upon the weather dispersed phase and dispersed medium are solids, liquids, or gases, there are eight types of the colloidal system possible.

Dispersion phase	Dispersion medium	Types of colloid	Examples
Solid	Solid	Solid sol	Some coloured glasses and gemstones
Solid	Liquid	Sol	Paints, cell fluids
Solid	Gas	Aerosol	Smoke, dust
Liquid	Solid	Gel	Cheese, butter
Liquid	Liquid	Emulsion	Milk, hair cream
Liquid	Gas	Aerosol	Fog, cloud
Gas	Solid	Solid sol	Foam rubber
Gas	Liquid	Foam	Froth, soap lather

 (ii) Nature of dispersed phase and dispersion medium: colloids are classified based on this category as follows:
(a) Aerosol: a liquid as dispersion phase in gas as dispersion medium is a colloidal solution. Example: fog
(b) Alcosol: a solid phase dispersed in alcohol as dispersion medium is a colloidal solution.
(c) Hydrosol: a solid phase dispersed in water as dispersion medium is a colloidal solution.
(d) Benzosol: a solid phase dispersed with benzene as dispersion medium is a colloidal solution.
(iii) Interaction between the dispersed phase and dispersion medium:
When the dispersion phase and dispersion medium interact then colloids are classified into lyophilic sols and lyophobic sols.
The dispersed phase particles have a great affinity for the dispersion medium in lyophilic sols, Which are reversible. Examples are gum, gelatin, starch, proteins, etc.
The dispersed phase particles have no affinity for the dispersion medium in lyophobic sols, which are irreversible. Examples are solutions of metals such as gold, silver, and metal hydrides.

Note: A gas mixed with other gas forms a homogeneous mixture; hence this system is not a colloidal system. The hydrophilic sols are more stable than hydrophobic sols because the stability of hydrophobic sols is due to charge only and hydrophilic sols are stable due to charge and solvation.