1.Matter changes state when energy is added or taken away. Most matter changes because of heat energy. ... When matter is heated enough, the molecules move faster and with greater energy. If enough heat is added, a solid can become liquid and a liquid can become gas.
Changing states of matter occur when matter loses or absorbs energy. When a substance absorbs energy the atoms and molecules move more rapidly and this increased kinetic energy pushes particles far enough, that they change form.