Phase transmitters absorb or emit large amounts of material called ambient heat when their body position changes. The material again liquefies from the solid. The substance changes from gas to liquid. Evaporation: The substance changes from a liquid to a gas. The converted to the liquid state without moving directly into the gas. There are many factors to consider when choosing a phase change material. A better PCM will have higher thermal conductivity, higher thermal conductivity, higher specific heat and density and longer reliability. When repeated Cycling, The material undergoes a phase change and changes from one form to another. Melting, freezing, evaporation and condensation are examples of phase changes. Phase change materials are effective because the fuse solidifies at a specific, defined temperature and is suitable for temperature control. Molten materials are more efficient at absorbing thermal energy compared to sensitive thermal energy materials. Examples of phase changes are melting, freezing, condensing, evaporation and sublimation. Abstraction involves the conversion of a gas into a liquid.