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

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

Answer: (D)

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 a 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 (solid, liquid, gas) without altering the chemical composition.
4. Compare the options given and note that 'Change in color,' 'Production of a gas,' and 'Formation of a precipitate' are all signs of chemical changes, while 'Change in state' is not.
5. Conclude that the correct answer is 'Change in state' because it is a physical change, not a chemical change.