A reaction that releases heat is known as an exothermic reaction.
Reactions can be classified as either exothermic or endothermic depending on whether they release or absorb heat from the surrounding.
A reaction that absorbs or gains heat from the surrounding is known as endothermic reaction.
On the other hand, if a reaction releases heat to the surrounding is known as exothermic reaction.
An exothermic reactions results to an increase in temperature of a solution while an endothermic reaction results to a decrease in the temperature of a solution.