ABSTRACT
Heat is a form of energy that is present in all matter. It is important in human energy use, biologically and throughout the natural environment. Heat is a measure of the thermal energy of vibrating molecules. The hotter a substance is, the more its molecules vibrate. As heat is a fonn of energy, it is measured in joules, and can be converted into other energy forms such as motion or electricity. It is governed by the First Law of Thermodynamics, which is the law of conservation of energy - that energy (as heat or other forms) can never be created or destroyed. Refrigerators and air conditioners use the exchange of latent heat in their circulating coolant fluid (or refrigerant) to operate. A compressor liquefies the refrigerant, then pumps it into the cooling circuit where it is allowed to expand and evaporate.
