Does a change in energy always indicate that a chemical reaction has taken place?

• A. A change in energy is unrelated to chemical or physical changes.
• B. Only endothermic changes in energy indicate a chemical reaction.
• C. No, a change in energy can occur without a chemical reaction, such as during physical changes.
• D. Yes, any change in energy means a chemical reaction has occurred.

Answer: (C)

Verified step by step guidance

1. Understand that energy changes can occur in both chemical and physical processes. Energy change alone does not confirm a chemical reaction.
2. Recall that a chemical reaction involves breaking and forming chemical bonds, which often involves energy changes (either absorption or release).
3. Recognize that physical changes, such as melting, boiling, or dissolving, also involve energy changes but do not alter the chemical identity of the substance.
4. Analyze the given options and identify that only some energy changes correspond to chemical reactions, while others correspond to physical changes.
5. Conclude that a change in energy does not always indicate a chemical reaction; it can also be associated with physical changes.