Which of the following best defines an exothermic reaction?

• A. A chemical reaction in which the temperature of the surroundings decreases.
• B. A chemical reaction that absorbs heat from its surroundings.
• C. A chemical reaction that requires continuous input of energy.
• D. A chemical reaction that releases heat to its surroundings.

Answer: (D)

Verified step by step guidance

1. Understand the definition of an exothermic reaction: it is a chemical reaction that releases heat to its surroundings.
2. Recall that when heat is released, the temperature of the surroundings increases, not decreases.
3. Recognize that a reaction absorbing heat from its surroundings is called an endothermic reaction, which is the opposite of exothermic.
4. Note that a reaction requiring continuous input of energy is typically non-spontaneous or endothermic, not exothermic.
5. Therefore, the best definition of an exothermic reaction is one that releases heat to its surroundings.