Concept:Surface tension is the force acting on the surface of a liquid that makes it behave like a stretched elastic film.
This force depends on the cohesive forces between liquid molecules.
Explanation:As temperature increases, the molecules of the liquid gain more kinetic energy.
They move faster and are able to break away from each other more easily.
This weakens the intermolecular attractive forces at the surface.
Since surface tension is caused by these cohesive forces, a weaker attraction means lower surface tension.
Therefore, heating the liquid reduces its surface tension.
Other factors, like adding soap or detergent, also reduce surface tension.
So the correct relationship is that surface tension decreases when temperature increases.
Answer:A. decreases