Here's the breakdown of state changes at melting and boiling points:

* Melting Point: When a substance reaches its melting point, it undergoes a solid to liquid phase change. This is also known as fusion. Think of ice melting into water.

* Boiling Point: When a substance reaches its boiling point, it undergoes a liquid to gas phase change. This is also known as vaporization. Think of water boiling into steam.