Which of the following describes a reaction that releases heat to its surroundings?

• A. Exothermic reaction.
• B. Endothermic reaction.
• C. Catalyst-driven reaction.
• D. Inhibitor-driven reaction.

Answer: (A)

Heat flow during a reaction shows whether energy is released as heat or absorbed. An exothermic reaction releases heat to its surroundings, so the starting energy of the reactants is higher than the energy of the products, and the difference appears as heat; the surroundings get warmer and the enthalpy change is negative. Endothermic reactions do the opposite, taking heat from the surroundings and cooling them, with a positive enthalpy change. Catalysts and inhibitors affect how fast a reaction goes, not how much heat is released or absorbed. So describing a reaction that releases heat to its surroundings aligns with an exothermic process.