Surface tension in a liquid is due to :
(1) Adhesive force between molecules
(2) Cohesive force between molecules
(3) Gravitational force between molecules
(4) Electrical force between molecules
Answer: (2) Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by the cohesion of similar molecules and is responsible for many of the behaviours of liquids. It is revealed, for example, in the floating of some objects on the surface of the water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface.
