What is a general characteristic of an exothermic reaction?

In an exothermic reaction, the defining characteristic is that it releases heat into the surroundings. This release of energy typically occurs because the energy of the products is lower than the energy of the reactants, often resulting in an increase in temperature of the surrounding environment. Common examples of exothermic reactions include combustion reactions, such as burning wood or fossil fuels, where heat and light are emitted.

Understanding exothermic reactions is crucial in various fields, from chemistry to engineering and environmental science. The heat released can be harnessed for practical applications, such as in heating systems or engines.

The other options highlight characteristics that do not apply to exothermic reactions: absorbing heat describes endothermic reactions; irreversible reactions can occur in both exothermic and endothermic processes but are not a defining trait; and the production of gas can happen in various types of reactions, not specifically limited to exothermic ones.