Question

The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must happen at the molecular level?
The molecules move more quickly and their average kinetic energy increases.
The molecules move more slowly and their average kinetic energy decreases.
The molecules move more quickly and their average kinetic energy decreases.
The molecules move more slowly and their average kinetic energy increases.

Answer 1

The molecules move more slowly and their average kinetic energy decreases.

Explanation: Temperature is a measure of the average kinetic energy of particles. A drop from 50°C to 30°C means the particles lose kinetic energy and therefore move more slowly.