Which statement best describes the difference between endothermic and exothermic reactions?

• A. Endothermic reactions absorb heat from the surroundings, while exothermic reactions release heat to the surroundings.
• B. Endothermic reactions decrease the temperature of the surroundings, while exothermic reactions increase it.
• C. Exothermic reactions require energy input, while endothermic reactions occur spontaneously.
• D. Endothermic reactions always produce light, while exothermic reactions do not.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the definitions of endothermic and exothermic reactions. Endothermic reactions absorb heat energy from their surroundings, causing the surroundings to lose heat.
2. Step 2: Recognize that exothermic reactions release heat energy to their surroundings, which causes the surroundings to gain heat.
3. Step 3: Connect the heat flow to temperature changes: when a reaction absorbs heat (endothermic), the temperature of the surroundings decreases; when a reaction releases heat (exothermic), the temperature of the surroundings increases.
4. Step 4: Evaluate the incorrect options by considering the energy flow and spontaneity: exothermic reactions do not necessarily require energy input, and endothermic reactions do not always occur spontaneously.
5. Step 5: Conclude that the best description is that endothermic reactions absorb heat from the surroundings, while exothermic reactions release heat to the surroundings, which aligns with the fundamental thermodynamic definitions.