Surface tension is defined as the force acting per unit length perpendicular to the line drawn on the surface of liquid. It is denoted by Greek letter γ (Gamma). The energy required to increase the surface area of the liquid by one unit is defined as surface energy. It has dimensions of kg s-2 and in SI unit it is expressed as N m-1. The lowest energy state of the liquid will occur when surface area is minimum. Spherical shape satisfies this condition.Thus, liquid drops are spherical in shape at lower energy. It is surface tension which gives stretching property to the surface of a liquid. The magnitude of surface tension of a liquid depends on the attractive forces between the molecules.
