What causes matter to change states

Adding energy to matter causes a physical change-matter moves from one state to another. For example, adding thermal energy-heat-to liquid water causes it to become steam or vapor-a gas. Taking away energy also causes physical change, such as when liquid water becomes ice-a solid-when heat is removed.

You have too either melt the object or freeze the object for example you have a cup of water than u put it in the freezer an hour from now it is a solid see? You went to liquid to solid