When does a chemical reaction release energy?

A chemical reaction releases energy during an exothermic reaction. In this context, exothermic reactions are defined as processes that release energy in the form of heat or light to the surroundings. During such reactions, the total energy of the products is lower than that of the reactants, which results in the release of excess energy. This release often causes the surrounding temperature to increase.

In contrast, endothermic reactions absorb energy from their surroundings, leading to a drop in temperature of the surroundings. When reactions occur at constant temperature, it indicates that there is no net energy being absorbed or released, which is not the same as releasing energy. The mention of reactants being at a lower energy level is also misleading; energy levels of reactants don't determine the energy change; rather, it is the comparison of energy levels between reactants and products that determines whether energy is released or absorbed. Thus, exothermic reactions clearly exemplify the concept of energy release in chemical processes.