A reaction that gives off energy to the surroundings is called

• A. Exothermic
• B. Endothermic
• C. Catalytic
• D. Irreversible

Answer: (A)

Exothermic describes a reaction that releases energy to the surroundings. This energy release shows up as heat (and sometimes light), so the surroundings get warmer. The idea is that the reactants start with more energy than the products, and the excess energy leaves the system. In contrast, endothermic reactions absorb energy from the surroundings, which is why they feel cold. Catalysis involves a substance that speeds up the reaction without changing the overall energy change, and irreversible refers to whether the reaction can be easily reversed—not to energy transfer. So, the word that fits is exothermic.