Which of the following is NOT a possible sign of a chemical change?

• A. Change in state (e.g., melting or boiling)
• B. Change in color
• C. Production of a gas
• D. Formation of a precipitate

Answer: (A)

Verified step by step guidance

1. Understand that a chemical change involves the formation of new substances with different properties, while a physical change affects only the state or appearance without changing the substance's identity.
2. Identify common signs of chemical changes, which include change in color, production of a gas, and formation of a precipitate, as these indicate new substances are formed.
3. Recognize that a change in state, such as melting or boiling, is a physical change because it involves a change in the physical form of the substance without altering its chemical composition.
4. Compare the options given: change in color, production of a gas, and formation of a precipitate are all signs of chemical changes, whereas change in state is not.
5. Conclude that the sign which is NOT indicative of a chemical change is the change in state (e.g., melting or boiling), as it represents a physical change.