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.

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

Explanation:

The temperature of a sample of liquid water changes from 50°C to 30°C, at the molecular level, the molecules moves more slowly and their average kinetic energy decreases.

In this problem, we have reduction in temperature.

This implies that the amount of thermal energy supplied to the water has reduced.

Thermal energy is directly proportional to the motion of the particles of a medium.

The greater the thermal energy the faster the particles begins to move.

Therefore, when the temperature reduces, this is like cooling.

The average kinetic energy decreases and molecules are slow.

Kinetic energy is due to the motion of particles.