When heat energy is added two changes are observed: change a: solid changes phases to a liquid change b: liquid changes phases to a gas what are the names or phase changes in a and b

A is melting. Melting occurs when the molecules of a solid speed up enough that the motion overcomes the attractions so that the molecules can move past each other as a liquid.

b is evaporation The molecules move and vibrate so quickly that they escape into the atmosphere as molecules of water vapor