Question

Why surface tension is zero at critical temperature?

Answer 1

The rule of thumb is that surface tension decreases with the increase of temperature, reaching a value of zero at the critical temperature. ... The density, molar mass and the critical temperature of the liquid have to be known. At the critical point the surface tension is always zero.

Answer 2

$\huge \fbox \red{Answer}$

Surface tension of a liquid is zero at critical point. The surface tension of a liquid decreases with increase of temperature and becomes zero at its critical temperature (where the surface of separation between liquid and its vapour dispapears).