Answer to Question #161 in Molecular Physics | Thermodynamics for Anna

Question

Show, that near absolute zero surface tension of liquid does not depend on temperature, that is lim(dσ/dT) (T→0). Specifically it refers to helium - the only substance which stays liquid under absolute zero temperature.

Answer 1

Let’s try to use the formula q=TΔS, where ΔS - increase of entropy of film under increase of its surface on one point. One gets dσ/dT=-ΔS. According to Nernst theorem under absolute zero temperature all processes happen without change of entropy, that is ΔS=0.