# Does surface tension change with concentration?

##### 1 Answer

Yes

Derivation

dG=

At constant temperature and pressure,

dG=

n=no. of moles of the surfactant

so,G=

by comparing the two equations (1) & (2) for dG, we get

Now for an interface in which oil and water for example, are separated by a geometrically flat surface.The approximation implies that on the surfactant S accumulates at the surface and hence that

The equation becomes

for dilute solutions,

therefore at constant temperature,

I've tried to make the derivation look as simple as possible.If still not understood , leave a comment below.