The surface tension of liquid decreases with rise of temperature. The surface tension of liquid is zero at its boiling point and it vanishes at critical temperature. $\quad$ At $\quad$ critical $\quad$ temperature intermolecular forces for liquid and gases becomes equal and liquid can expand without any restriction. For small temperature differences, the variation in surface tension with temperature is linear and is given by relation
$$
T_{t}=T_{0}(1-\alpha t)
$$
where $T_{t}, T_{0}$ are the surface tension at $t^{\circ} \mathrm{C}$ and $0^{\circ} \mathrm{C}$ respectively and $\alpha$ is the temperature coefficient of surface tension.