In the absence of external forces, drops of liquid are always spherical in shape. If you drop small amount of mercury from a small height, it spreads in small spherical globules. The water drops falling from a tap or shower are also spherical.

All the above experiences are due to a characteristic property of liquids, which we call surface tension.

Inter-Molecular Forces

The inter-molecular forces are of two types: cohesive and adhesive. Cohesive forces characterize attraction between the molecules of the same substance, whereas force of adhesion is the attractive force between the molecules of two different substances. It is the force of adhesion which makes it possible for us to write on this paper. Gum and Fevicol show strong adhesion.