The potential energy associated with surface tension is much like the elastic potential energy of a stretched spring or a balloon. Suppose we do work on a puddle of liquid, spreading it out through a distance of Δs along a line L perpendicular to the force?
(a) What is the work done on the fluid surface in terms of (, Ls, and Δ?
(b) The work done is equal to the increase in surface energy of the fluid. Show that the increase in energy is proportional to the increase in area.
(c) Show that we can think of g as the surface energy per unit area.
(d) Show that the SI units of surface tension can be expressed either as N/m (force per unit length) or J/m2 (energy per unit area).

AA =L As