Answer: An exothermic reaction is a "reaction for which the overall standard enthalpy change ΔH⚬ is negative." Exothermic reactions usually release heat and entail the replacement of weak bonds with stronger ones.
Exothermic reactions are important to forensic sciences and particularly to fire and explosion investigation. When a chemical reaction requires heat (rather than producing it) and results in cooling down the surroundings, it is conversely called endothermic.
Example-
Respiration is a series of exothermic reactions that occur in the mitochondria of living cells in order to release energy from food molecules. This energy can then be used to produce heat, for movement, growth, reproduction and active uptake.
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