When a solid is heated, particles vibrate rapidly as their temperature rises. Then particles break free from the forces holding them in place. In this process, called melting, solids change into liquids. If a liquid is heated, particles will escape and form a(n) gas. This transformation of liquid to gas is called vaporization. Particles in the gaseous state are spread out because they have freedom of motion. As energy is removed from gases, they turn into liquids during condensation. Removing energy from liquids cause them to freeze, or turn into solids. If liquids are boiled, bubbles of vapor escape. A substance’s temperature doesn’t change while a change of state occurs.