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

• A. Change in state (such as melting or boiling)
• B. Production of a gas
• C. Change in color
• 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 the options given: production of a gas, change in color, formation of a precipitate, and change in state (such as melting or boiling).
3. Recall that production of a gas, change in color, and formation of a precipitate are all indicators of a chemical change because they suggest new substances are formed.
4. Recognize that a change in state (melting or boiling) is a physical change because it involves a change in the physical form of the substance without altering its chemical composition.
5. Conclude that the option 'change in state (such as melting or boiling)' is NOT a sign of a chemical change.