Which statement best describes the law of conservation of energy as it applies to chemical reactions?

• A. Energy is always lost as heat during a chemical reaction, resulting in a decrease in total energy.
• B. Energy is only conserved in physical changes, not in chemical reactions.
• C. Energy can be created from matter during a chemical reaction, increasing the total energy.
• D. Energy cannot be created or destroyed; in a chemical reaction, the total energy of the system and surroundings remains constant.

Answer: (D)

Verified step by step guidance

1. Understand the law of conservation of energy: it states that energy cannot be created or destroyed, only transformed from one form to another.
2. Apply this principle to chemical reactions, where energy changes form (e.g., chemical potential energy to heat or light) but the total energy remains constant.
3. Recognize that during a chemical reaction, energy may be released or absorbed, but the sum of energy in the system plus its surroundings does not change.
4. Evaluate the given statements by comparing them to the law: statements claiming energy loss without compensation, creation of energy, or restriction to physical changes contradict the law.
5. Conclude that the correct description is that energy cannot be created or destroyed; the total energy of the system and surroundings remains constant during a chemical reaction.