What are the three phase changes that require energy to perform?
Fusion (melting), vaporization, and sublimation
When a substance changes states, it requires energy when it goes to a higher energy state and releases energy when it goes to a lower energy state. Gas has a higher energy than liquid and liquid has a higher energy than solid. The three state changes from a lower energy to a higher energy are:
solid to liquid: fusion
liquid to gas: vaporization
solid to gas: sublimation