Match the following:
(i) Foam            (a) smoke
(ii) Gel              (b) cell fluid
(iii) Aerosol       (c) jellies
(iv) Emulsion     (d) rubber
                          (e) froth
                          (f) milk

Colloids are classified on the basis of the physical states of the dispersed phase and the dispersion medium.

A foam is a colloidal system in which a gas is dispersed in a liquid. A common example is froth. Hence,

$$(i)\rightarrow(e).$$

A gel is a colloidal system in which a liquid is dispersed in a solid. A common example is jellies. Hence,

$$(ii)\rightarrow(c).$$

An aerosol is a colloidal system in which a solid or liquid is dispersed in a gas. Smoke is an example of a solid dispersed in a gas. Hence,

$$(iii)\rightarrow(a).$$

An emulsion is a colloidal system in which a liquid is dispersed in another liquid. Milk is a typical example of an emulsion in which fat droplets are dispersed in water. Hence,

$$(iv)\rightarrow(f).$$

Therefore, the correct matching is:

• (i) Foam → (e) Froth
• (ii) Gel → (c) Jellies
• (iii) Aerosol → (a) Smoke
• (iv) Emulsion → (f) Milk

Hence, the correct sequence is (i)-(e), (ii)-(c), (iii)-(a), (iv)-(f).