Surface Tension

[logearav]

When we consider a beaker of water and two molecules, one completely inside the water and the other at the free surface, the water molecule at the free surface will experience net downward force of attraction and this causes the water molecule to behave like a stretched membrane, which is called as surface tension.

Now to bring this molecule at the free surface to interior of beaker, one has to do work against the force of attraction and this is stored as potential energy. Water molecule acquires minimum surface area to have minimum potential energy. What is the relation between surface area and potential energy?

More work done so more potential energy and more surface area. But how surface tension correspond to minimum potential energy. I can't understand.

Edited November 24, 2011 by logearav

[Enthalpy]

You work against the attractive Van der Waal's force to bring a molecule to the surface, and this added molecule increases the area of the liquid. The ratio between the added work and the added area is the tension.

 

Molecules go where they're attracted to, or in other words minimize their energy, by diving into the liquid where they have more neighbours. By doing so, they reduce the liquid's area.