Most substances can exist as a solid, liquid or gas.
These three forms are called phases. A substance can be changed from one phase to another by adding or removing heat. A change from one phase to another is called a phase change. The most remarkable feature of any phase change is that it occurs at a constant temperature, as energy is being added or removed. It appears to work like a cordless heating pad, providing comfortable heat up to three times longer than any other product on the market.