How does the molecular motion of a substance change when it goes from liquid to gas?

Question

A.
The molecules lose energy and their relative motion increases.

B.
The molecules gain energy and their relative motion increases.

C.
The molecules lose energy and their relative motion decreases.

D.
The molecules gain energy and their relative motion decreases.

Answer 1

The correct answer is:

B. The molecules gain energy and their relative motion increases.

When a substance transitions from liquid to gas (a process called vaporization or evaporation), the molecules gain energy, typically from heat, which allows them to overcome intermolecular forces holding them together in the liquid state. As they gain energy, their relative motion increases significantly, leading to the more dispersed and free-moving state characteristic of gases.