Question

An emulsion is a colloidal system of___________
(A) two solids
(B) two liquids
(C) one gas and one solid
(D) one gas and one liquid

Answer 1

Hint: An emulsion is a type of mixture made by combining two liquids that normally don't mix. An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of other liquids.

Complete step by step solution:
The word emulsion has originated from the Latin word meaning "to milk" (milk is one example of an emulsion of fat and water). The process of turning a liquid mixture into an emulsion is called emulsification.
An emulsion is a type of colloid that can be formed by combining two liquids that normally don't mix.
In an emulsion, one liquid contains a dispersion of the other liquid.
The process of mixing liquids to form an emulsion can be defined as emulsification.
Even the liquids that form them may be clear, emulsions appear cloudy or coloured because the light is scattered by the suspended particles present in the mixture.
Some examples of emulsions are:
Butter(an emulsion of water in fat), the yolk of an egg (emulsion containing the emulsifying agent lecithin), Crema(emulsion consisting of water and coffee oil), mayonnaise (oil in water emulsion that is stabilized by the lecithin in egg yolk).
A substance that stabilizes an emulsion can be defined as emulsifier or emulgent. Emulsifiers work by increasing kinetic stability of a mixture. Surfactants are one type of emulsifiers. Detergents are an example of surfactant. Other examples of emulsifiers include lecithin, mustard, soy lecithin, diacetyl tartaric acid ester of monoglyceride (DATEM), and sodium stearoyl lactylate.

Note: Sometimes the terms "colloid" and "emulsion" are used as the same, but the term emulsion is appropriate when both phases of a mixture are liquids. The particles in the colloid can be any phase of matter. Therefore an emulsion is a type of colloid, but not the vice versa.