Answer:
The molecules gain energy.
The space between the molecules increases.
Explanation:
A solid's molecules vibrate and are very close together.
A liquid's molecules slide and are further apart than those of a solid.
When a solid melts into a liquid, the molecules drift apart and are able to move around. The process also requires energy, so the molecules gain energy in order to change states. Therefore, the molecules gain energy and the space between them increases.
