Question

What type of colloidal system is fog?
A.Gas in liquid
B.Liquid in gas
C.Liquid in liquid
D.Solid in gas

Answer 1

To answer this question, recall the definition of colloids. A colloidal solution is defined as a homogeneous and a non-crystalline substance, in which large molecules of one substance are dispersed through a second substance.

Complete Step by step answer:
The particles of a colloid are always in a constant set of motion and do not settle due to continuous collisions. These cannot be separated by ordinary filtering or centrifuging like those in a suspension. A colloid is different from a solution as in a solution, solute and solvent are a part of single-phase, whereas in a colloid the dispersed phase and a continuous phase are part of different phases and separated by phase separation. The dispersed-phase particles are generally visible in an optical microscope. Colloids also show the property of the Tyndall effect which is defined as the scattering of light by particles in the colloid. Overall, the colloids with their dispersion phase and dispersion media can be summarized as follows:

Dispersed phase	Dispersion medium	Type of colloid	Example
Solid	Solid	Solid sol	Colored glass and gemstones
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 stones, foam rubber
Gas	Liquid	Foam	Froth, whipped cream, soap-lather

From the above figure, it is pretty evident that fog is an example aerosol i.e. liquid dispersed in gas.

Hence, we can conclude that the correct answer to this question is option B.

Note: Emulsions can be formed by mechanical means, such as agitation, provided that the liquids that are mixed have no mutual solubility. Mechanical stability is an integral part of colloidal solutions and is imparted by agents that form films at the surface of the droplets e.g., soap molecules, colloidal carbon or bentonite. Stable emulsions can be destroyed by inactivating or destroying the protective agent. A student can confuse Oil in water (o/w) type and Water in oil (w/o) type. Make sure you remember that in oil in water (O/W) emulsion, the oil will be the dispersed phase and water will be the dispersion medium while in water in oil (w/o) type, water will be the dispersed phase and oil will be the dispersion medium.