Question

At critical temperature, What is the surface tension of a liquid ?

Answer 1

Surface tension is related to temperature; for that reason, when a value is given for the surface tension of an interface, temperature is also specified. The rule of thumb is that surface tension decreases with the increase of temperature, reaching a value of zero at the critical temperature. This enables the prediction of the surface tension of an arbitrary liquid pure substance at all temperatures. 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.