Question

With an increase in temperature, surface tension of liquid (except molten copper and cadmium)

• A. increases
• B. remain same
• C. decreases
• D. first decreases then increases

Answer 1

Answer: (C)

decreases

Answer 2

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. At critical temperatureintermolecular 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 $t^{\circ} C$ and $0^{\circ} C$ respectively and $\alpha$ is the temperature coefficient of surface tension.