Exothermic reaction?

• A. A chemical reaction that releases energy to its surroundings.
• B. A chemical reaction that absorbs energy.
• C. A reaction that requires catalysts.
• D. A reaction that does not involve energy transfer.

Answer: (A)

Exothermic reactions release energy to their surroundings, usually as heat, which is why the surroundings get warmer. This means the reaction has a negative enthalpy change (ΔH < 0).

That’s exactly what the statement describes: a chemical reaction that releases energy to its surroundings. The other ideas don’t define exothermic behavior. A reaction that absorbs energy describes an endothermic process, not exothermic. A reaction that requires catalysts speaks to reaction rate (how fast it happens), not the energy change involved. And a reaction that does not involve energy transfer isn’t accurate, since all chemical reactions involve some transfer of energy as bonds break and form.