Question

Derivation of relation between surface energy and surface tension

Answer 1

Surface energy is defined as the amount of the work done against the force of surface tension, in forming the liquid surface of a given area at a constant temperature.

To obtain a expression for surface energy, take a rectangular frame ABCD having a wire PQ which can slide along the sides AB and CD. Dip the frame in soap solution and form a soap film BCQP on the rectangular frame. There will be two free surfaces of film where air and soap are in contact.



If temperature of the film remains constant in this process, this work done is stored in the film as its surface energy