Difference: Exothermic and Endothermic Reactions

Every chemical reaction comes with an energy transformation. Depending on whether heat or thermal energy is released or absorbed into the environment during the reaction, the reaction is called an exothermic or an endothermic reaction.

In this article I would like to explain these two types of chemical reactions and give some examples for the individual reaction types.

Exothermic Reactions

During an exothermic reaction, heat or thermal energy is released to the environment.

Example: An example of an exothermic reaction is the combustion (burning) of gas, petrol, coal or other energy sources.

Endothermic Reactions

During an endothermic reaction, energy is absorbed from the environment. Therefore, endothermic chemical reactions can only be sustained as long as energy is supplied from the outside. As soon as this external energy supply stops, the chemical reaction which has taken place comes to a standstill.

Example: An example of an endothermic reaction is to split water into its components oxygen and hydrogen with the help of electric current. Also the dissolution of effervescent powder (citric acid and sodium bicarbonate) in water is an endothermic reaction. The water gets colder, because the necessary energy is drawn out of the water.