What is surface tension? Characteristics of surface tension?

Definition:
Surface tension is the force acting along the surface of a liquid that keeps the liquid surface in a state of tension and allows the liquid droplets to contract to the smallest possible area with spherical conformation.

Characteristics of surface tension:

• A molecule in the interior of a liquid is completely surrounded by other molecules and so, attracted equally in all directions.
• On a molecule in the surface of liquid however, there is a resultant attraction inwards and because
  of this inward puli, the surface of the liquid always tends to contract to the smallest possible area.
• It is for this reason of inward pull, the drops of liquid become spherical as far as feasible to a minimum surface area.
• As a result of this spontaneous tendency to contract, the surface of liquid behaves as if it were in a state of tension like a stretched elastic membrane.
• To expand the area of the surface of a liquid, it is necessary to bring out the molecules from the bulk of liquid (interior) on to the surface, against the inward pull (surface tension). This can be done by adding surface tension lowering agents into the solution.