For most ordinary liquids at temperatures well below their critical temperature, how does surface tension generally change when temperature is increased?
Options

Question

For most ordinary liquids at temperatures well below their critical temperature, how does surface tension generally change when temperature is increased?

G1 Physics · Accepted Answer

Increasing temperature increases molecular agitation. The difference between the energetic environment of surface molecules and bulk molecules becomes smaller. Therefore the surface free energy per unit area and hence the surface tension generally decrease as temperature rises. At the critical temperature, the distinction between liquid and vapour disappears and surface tension approaches zero rather than infinity. Correct option: B.