What happens to acetone molecules when you add heat to a beaker of liquid acetone? They gain a higher average kinetic energy. They rearrange into a more ordered state. They get closer together. They move more slowly.
When you heat up most substances it gives them more Kinetic energy and the substance becomes less arranged in an ordered state, further apart and move faster. therefore the answer is the first: They gain a higher average kinetic energy Hope that helps :)