The sun produces heat from nuclear reactions deep inside it. All life on the earth depends on this heat.

Friction -- the rubbing of one object against another -- produces heat. Survivalists (and Boy Scouts) learn to start a fire with friction.

Chemical reactions produce heat by causing a chemical change in substances. The fire of a match is the result of a chemical reaction.

The Earth contains much heat deep inside. Some of this heat escapes to the surface when a volcano erupts.

Source

The World Book Encyclopedia Chicago: World Book-Childcraft International, Inc., 1979

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This page was last updated on 08/17/2018.