Phase change materials are materials that change from solid to liquid to gaseous and back again under the influence of temperature. An example is water that at 0°C changes from solid to liquid, and at 100°C changes from liquid to gaseous.
Phase change material refers to a material that can be used for the practical storage of thermal energy. The phase change used for energy storage is the change from solid to liquid and vice versa. When the material passes from one phase to another, a great deal of energy is released or absorbed. The temperature at which this change takes place depends on the material.