Question

How do emulsifying agents stabilise the emulsion?

Answer 1

Emulsions are colloidal dispersion or colloids. Between suspensions and solutions, there are particles which come under colloids. The range of diameters of colloidal particles is between 1 and 1000 nanometers. In this liquid is the dispersed phase and liquid is the dispersed medium.
The addition of any substance to solutions is needed only when the solutions are unstable without their addition.

Complete step by step answer:
First we should know why there is a need to add emulsifying agent in emulsion;
According to thermodynamics, an emulsion is an unstable system. This is because emulsions are liquid-liquid systems which have a natural tendency to separate and reduce its surface energy or interfacial energy (Interfacial free energy is the disruption of intermolecular bonds that occurs when a new surface is created).
Now, we will understand what addition of emulsifying agents do to the emulsions;
Emulsifiers, also known as emulsifying agents help in stabilizing an emulsion by reducing the interfacial tension or surface energy between two liquids forming the emulsion by forming a film between the medium and suspended particles. Emulsifying agents are the long-chain molecules with polar groups.

The few examples of emulsifying agents are

(1) Milk protein or Casein is an emulsifier as it forms a protective layer around fat molecules dispersed in water which reduces the interfacial tension and stabilizes the emulsion.

(2) Soap as an emulsifying agent. In this method, soap molecules form a protective film around each oil droplet which reduces the interfacial tension and stabilizes the emulsion.

Note: The process of making emulsion is known as emulsification. Emulsions are of two types: (i) oil in water type (ii) water in oil type.
Emulsions are diluted with the dispersion medium. The dispersed liquid when mixed in the solution forms a separate layer. The droplets in emulsions are generally negatively charged and can be precipitated by electrolytes. Emulsions are broken into constituent liquids by heating, centrifuging and freezing.