Endothermic reactions are reactions that are accompanied by the absorption of heat. As a result of endothermic reactions, heat is released, and as a result of exothermic reactions, heat is absorbed.
Endothermic reactions are numerous chemical reactions that occur when the temperature decreases or when the system cools. For example, when crystalline salt hydrate is dissolved in water, heat is released, which is called the heat of solution. When crystalline salts dissolve in water, a large amount of heat is released, so under natural conditions water has a high boiling point.