Question

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

Answer 1

Hint: The solution to this question can be obtained without knowing the theory of dispersion also. We know that smoke has the gaseous state but we can see the particles of smoke which are nothing but solid. This makes our conclusion easy.

Complete step by step solution:
-Dispersion is a system where particles of a certain phase are dispersed into a medium of another phase. There are three types of dispersions named solutions, colloids and suspensions. The solution is a homogeneous mixture of a material which is dispersed into another material such that they get completely mixed.
-A colloid is a heterogeneous mixture of particles which are small but the particles will not settle down if left for a particular period. It means that the particles will not undergo sedimentation.
-Suspension is a mixture of large particles which undergo the process of sedimentation when left for a particular period. It is also a heterogeneous dispersion. They can be physically separated from solutions and colloids.
-Many suspensions can be separated by a filter like sand in water, chalk in water. Colloids cannot be separated physically. Examples of colloids include butter, mayonnaise, paint. Colloids can be formed from solids, liquids and gases. Different phases of colloids can be classified with the help of a table as

	Dispersion medium
	gas	liquid	solid
Continuous medium	Gas	NONE	Liquid aerosolEg. Fog, mist	Solid aerosolEg. Smoke, dust
	Liquid	FoamEg. Whipped cream	EmulsionEg. Milk, butter	SolEg. Paint, ink, blood
	solid	Solid foamEg. aerogel	GelEg. cheese	Solid solEg. ruby

Thus the correct option is (C) solid dispersed in the gas.

Note: Our eyes cannot distinguish between colloids and solutions. This is because the dispersed particles can be too small to be visible by the naked eye. They are distinguished based on a phenomenon called the Tyndall Effect. It is difficult to classify the substances as the solution, colloid and suspension.