Chemical reactions involve energy transfers.
Many chemical reactions involve the release
of energy. For other chemical reactions to
occur, energy must be supplied.
When chemical reactions occur, energy is transferred
to or from the surroundings.
An exothermic reaction is one
that transfers energy to the
surroundings. Examples of
exothermic reactions include
combustion, many oxidation
reactions and neutralisation.
Everyday uses of exothermic
reactions include self-heating
cans and hand warmers.
An endothermic reaction is one
that takes in energy from the
surroundings. Endothermic
reactions include thermal
decompositions. Some sports
injury packs are based upon
endothermic reactions.
If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction.
The same amount of energy is transferred in each case.