Answer: increases
Explanation:
Matter exists in three different states, they are solids, liquids and gases. And each of them contains molecules with a certain amount of kinetic energy.
Hence, the addition of heat changes a substance from a liquid to a gas through a process called vaporization, whereby liquid molecules on changing to gases acquire a higher kinetic energy, and move more freely within the containing vessel.
Thus, the higher kinetic energy explains the increase in the average distance between molecules.
