Question

1. water is unique in that it exists in all three states on earth. which statement best describes what happens to the energy of the particles when water vapor begins to cool?

• a. the average potential energy decreases.
• b. the average kinetic energy decreases.
• c. the average potential energy remains the same.
• d. the average kinetic energy remains the same.

Explanation:

When water vapor cools, the temperature of the particles decreases. Temperature is a measure of the average kinetic energy of the particles. So, as temperature decreases, the average kinetic energy of the particles decreases. Potential energy is related to the phase change (e.g., from gas to liquid) and not directly to the cooling process (without a phase change). Since the question is about cooling (not a phase change), we focus on kinetic energy.

Answer:

B. The average kinetic energy decreases.