Physics 2016 JAMB Past Questions - Question 39: Which of the following does NOT cause a reduction of the surface tension of water ?

Correct Answer

D

Explanation

The following does NOT cause a reduction of the surface tension of water:

1. Increasing the temperature: Increasing the temperature of water actually decreases its surface tension. As the temperature rises, the kinetic energy of water molecules increases, causing them to move more vigorously and disrupt the cohesive forces at the surface, leading to a decrease in surface tension.

2. Adding a surfactant: Surfactants, such as soap or detergent, are known to reduce the surface tension of water. They contain molecules with hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, which disrupt the cohesive forces between water molecules at the surface, resulting in a lower surface tension.

3. Increasing the pressure: Increasing the pressure does not directly affect the surface tension of water. Surface tension is primarily determined by the cohesive forces between water molecules, which are not significantly influenced by changes in pressure.

4. Adding an inert solute: Adding an inert solute, such as salt or sugar, does not alter the surface tension of water. In fact, the presence of solutes generally has a negligible effect on the surface tension of water, as long as the solute does not have surfactant properties.

Therefore, increasing the pressure does not cause a reduction in the surface tension of water.