Advanced Placement (AP) Chemistry Practice Exam 2026 - Free AP Chemistry Practice Questions and Study Guide

In exothermic reactions, energy is released into the surroundings, which typically results in a rise in temperature. This release of energy is often associated with the formation of new bonds in the products. When these products are formed, the bonds are generally stronger than those in the reactants, resulting in a negative change in enthalpy (ΔH). The negative ΔH indicates that the system has lost energy to the surroundings, reinforcing the idea that energy is being released during the reaction. Therefore, identifying that exothermic reactions release heat and are characterized by a negative ΔH accurately reflects their nature.