Question Detail
Question
What causes the surface of a liquid to contract and behave like a stretched membrane?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Molecules inside a liquid experience cohesive forces equally in all directions. Surface molecules, however, have no liquid molecules above them, so they experience a net inward pull. This inward pull creates internal pressure and forces the surface to contract to the minimum area, resulting in surface tension.
Hint
Consider the difference in the molecular environment between a molecule in the bulk of the liquid and one at the surface.