Which statement describes an exothermic reaction?

• A. It absorbs heat from the surroundings
• B. It occurs only under pressure
• C. It releases heat to the surroundings
• D. It requires energy input to start

Answer: (C)

An exothermic reaction is one that releases heat to the surroundings. That means as the reaction happens, energy leaves the system as heat, making the nearby environment warmer. Saying it releases heat to the surroundings matches this defining behavior exactly.

Absorbing heat from the surroundings describes an endothermic process, where the system takes in energy and the surroundings may feel cooler. The idea that a reaction occurs only under pressure isn’t a defining feature of exothermicity, since reactions can happen across different pressures. Requiring energy input to start relates more to activation energy; a reaction can be exothermic and still need a spark or heat to begin, but once it starts it releases heat.