question_answer 17)

  How are the colloidal solutions classified on the basis of physical states of the dispersed phase and dispersion medium?

Answer:

Depending upon whether the dispersed phase and the dispersion medium are solids, liquid or gases, eight types of colloidal systems are possible. A gas mixed with another gas never forms a colloidal system.      

Dispresed phase	Dispersion medium	Type of colloid	Examples
Solid	Solid	Solid sol	Some coloured glasses and gem stones.
Solid	Liquid	Sol	Paints cell fluids
Solid	Gas	Aerosol	Smoke, dust
Liquid	Solid	Gel	Cheese, butter, jellies
Liquid	Liquid	Emulsion	Milk, hair cream
Liquid	Gas	Aerosol`	Fog, mist, cloud, insecticide- sprays
Gas	Solid	Solid sol	Pumice stone, foam rubber
Gas	Liquid	Foam	Forth, whipped cream, soap-lather

Out of the various types of colloids given above, the most common are sots (solids in liquid), gel (liquid in solids) and emulsions (liquids in liquids). (i) If the dispersion medium is water, the sol is called aquasol or hydrosol. (ii) If the dispersion medium is alcohol, it alcohol, it is called alcosol.