Energy is conserved in chemical reactions. The total amount of energy in the universe never changes. When a chemical reaction occurs, energy is transferred to or from the reaction’s immediate surroundings.
An exothermic reaction transfers energy to its surroundings. The temperature of its surroundings increases.
Exothermic reactions include:
An endothermic reaction takes in energy from its surroundings. The temperature of its surroundings decreases.
Endothermic reactions include:
An exothermic reaction between dilute sodium hydroxide and hydrochloric acid.