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     Heat is a form of energy which causes in us the sensation of warmth or coldness. For example when we stand near the fire or touch a metallic piece placed in the sum, we feel a sensation of hotness. Similarly, if we touch a lump of ice, the sensation is that of coldness. A body appears hot when our hand receives heat from it, while appears cold when heat passes from our hand to the body. So, the energy transferred from one body to another due to a temperature difference between them is called heat. The flow of this energy transfer is always from a body at higher temperature to a body at lower temperature.

     Heat produces a number of effects in material as well as in living bodies. Some of these effects are listed below :- 

Change in Temperature

Change in Dimensions

Change in State