Explain briefly about Foams  

Consider the following example. Take some liquid in a glass and agitate or shake it vigorously. What do you observe at the top of the liquid. Yes, a foam is formed. Foams are also considered colloidal dispersions. Foams are dispersions of gas or air bubbles in a liquid. Foam is created by agitation of a liquid with a consequent entrapment of air in the liquid film. Foam consists of more or less stable liquid-air interfaces, the air cells being surrounded by liquid films that constitute the continuous phase.

The foaming properties of liquids depend on their viscosity and low air-liquid surface tension. The gas bubbles are separated from each other by liquid walls called films or camellia, which are elastic.  The diameter of the foam bubbles range from about 1 mm to several centimeters.  Depending on the bubble size and wall thickness, dense or light foams are formed.