Heat, warmth or hotness is felt by us in our every day life in varying degrees of intensities. So far nothing has been found to be perdctly heatless. Scientifically heat is defined as a form of energy in transit. Thus heat is the total amount of kinetic energies of all molecules, ions and atoms of which the substance, object or body under consideration is composed. Like energy heat is also measured in Joule. Other units of heat are calorie and BTU. Heat always flows from a hot system to a cold system.