What is a characteristic of an exothermic reaction like neutralization?

An exothermic reaction is defined by its release of heat during the process. In the context of a neutralization reaction, which typically involves an acid reacting with a base to form water and a salt, the reaction releases energy in the form of heat. This release of heat manifests as an increase in temperature of the surrounding environment, indicating that energy is being transferred from the reaction system to the surroundings.

In contrast, reactions that absorb heat are characterized as endothermic, so those options that suggest absorption of heat or being endothermic are inaccurate descriptors for an exothermic reaction. The concept of maintaining a constant temperature is not applicable, as exothermic reactions generally cause changes in temperature due to the heat released. Thus, the defining characteristic of exothermic reactions, such as neutralization, is that they release heat, confirming the correctness of the answer.