What happens when liquid changes to gas? 1.Added heat makes water molecules move fast enough to overcome the attraction
between them
2. Heat causes molecules to speed up and merge together (Which one?)

#1

The temperature that this happens is called the freezing point and is the same temperature as the melting point. As more energy is put into the system, the water heats up, the molecules begin moving faster and faster until there is finally enough energy in the system to totally overcome the attractive forces.

Explanation:

#2

Heating a liquid increases the speed of the molecules. An increase in the speed of the molecules competes with the attraction between molecules and causes molecules to move a little further apart. ... A decrease in the speed of the molecules allows the attractions between molecules to bring them a little closer together.