In terms of heat energy, what distinguishes exothermic reactions from endothermic reactions?

Exothermic reactions are characterized by the release of heat energy to the surroundings. This process occurs when the total energy of the products formed is lower than the total energy of the reactants, resulting in a surplus of energy that is released as heat. Common examples of exothermic reactions include combustion and respiration, where energy is emitted during the reactions.

In contrast, endothermic reactions absorb heat energy from the surroundings, leading to a decrease in the temperature of the surrounding environment. This behavior occurs because the total energy of the products is higher than that of the reactants, necessitating an input of energy (usually in the form of heat) to drive the reaction.

Understanding this distinction is essential for studying thermochemistry and the energy changes that occur during chemical reactions, which can influence reaction rates and the conditions under which reactions occur.