What is surface energy? With a neat labelled diagram, derive the relation between
the surface tension and surface energy.
Answers
Explanation:
The energy associated with the intermolecular forces at the interface between two media the surface energy per unit area equals the surface tension. called also free surface energy.
Relation betweeen Surface Energy and Surface Tension :
Let us consider a rectangular wire frame PQRS, of which the arm RS is movable. The frame is dipped in a soap solution sothat a soap film is produced in the frame. The length of arm RS is/
and surface tension of liquid is T.
The total upward force acting on RS due to surface tension = 2T the factor 2 is due to a film has two surfaces.
To keep the wire in position, a force F= 2TLhas to be applied in thei downward direction.
Now. if the arm RS is pulled through a small distance x to the position R'S' keeping the temperature constant, then the work done by the external force = Fx=2T Lx
This work done forms the surface energy of the increased surface area.
Increase in surface area of the film = 2Lx
Surface energy =W /delta A
=2T Lx /2Lx
= T
Surface Energy = Thus, surface energy is numerically equal to the surface tension (under isothermal condition).
