What is the main difference between exothermic and endothermic reactions?

The main distinction between exothermic and endothermic reactions centers around the flow of heat during these chemical processes. In an endothermic reaction, heat is absorbed from the surroundings, resulting in a decrease in temperature in the immediate environment. This absorption of energy causes a positive change in enthalpy (ΔH > 0). Conversely, an exothermic reaction releases heat into the surroundings, which typically causes an increase in temperature in the environment. This release of energy results in a negative change in enthalpy (ΔH < 0).

Understanding this distinction is crucial in chemistry, as it helps predict the behavior of reactions under various conditions. Endothermic reactions often require an input of energy to proceed, while exothermic reactions can release energy, contributing to various applications, such as in thermodynamics and reaction kinetics. Recognizing that endothermic reactions are characterized by heat absorption and exothermic by heat release is essential for grasping these fundamental concepts in chemistry.