An exothermic reaction is a chemical reaction that releases heat. It is the opposite of an endothermic reaction.
Expressed in a chemical equation: reactants → products + energy
In thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the
form of heat. Its etymology stems from the Greek prefix endo-, meaning “inside” and the Greek suffix –thermic, meaning
“to heat”. The opposite of an endothermic process is an exothermic process, one that releases energy in the form of heat.
Source: WikepediA
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