What is an endothermic reaction?

An endothermic reaction is defined as a process that absorbs heat from its surroundings. In these types of reactions, the enthalpy (heat content) of the reactants is lower than that of the products, leading to an overall increase in heat as the reaction proceeds. This heat absorption can be felt as a drop in temperature in the surrounding environment, making it easy to identify an endothermic process.

During an endothermic reaction, energy is required to break bonds in the reactants before new bonds can form in the products. Common examples of endothermic reactions include photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen, and the dissolution of certain salts in water, such as ammonium nitrate.

In contrast, a reaction that releases heat energy occurs in exothermic reactions. The speed of a reaction does not determine if it’s endothermic or exothermic; it merely indicates the rate at which the reaction occurs. Irreversibility also does not define an endothermic process; both endothermic and exothermic reactions can be reversible or irreversible based on their reaction mechanisms. Thus, the characteristic of absorbing heat energy clearly defines what an endothermic reaction is.