What does one mean by exothermic and endothermic reactions? Give examples.

Exothermic reaction: Reactions in which heat is released along with the formation of products are called exothermic reaction.

For example: Burning of fuel is an example of exothermic reaction. When methane is burnt in the air, heat is produced along with carbon dioxide and water.

Endothermic reaction: Reactions in which energy is absorbed are known as endothermic reactions.

Decomposition reactions are example of endothermic reactions because they require energy in the form of heat, light or electricity for breaking down the reactants.

Example: Sliver chloride turns grey in sunlight to form silver metal.