Concept:Soap lather is a colloidal system where gas is dispersed in a liquid, making it a foam.
Explanation:A colloid is a mixture in which fine particles of one substance are dispersed uniformly throughout another substance.
When soap is agitated with water, air gets trapped inside the soap solution.
The soap molecules stabilise these trapped air bubbles by forming a film around them.
As a result, a large number of tiny gas bubbles are produced, giving a frothy mass.
Here, the dispersed phase is gas and the dispersion medium is liquid.
Such a colloidal system, where gas is dispersed in a liquid, is specifically called foam.
The other options are incorrect because a solid sol contains solid particles in a liquid, an emulsion contains liquid dispersed in another liquid, and an aerosol contains liquid or solid particles dispersed in a gas.
Answer:Soap lather is a foam.
Correct option: C. Foam