Which of the following is a clue that a chemical change has occurred?

• A. Formation of a gas
• B. Change in state from solid to liquid
• C. Dissolving sugar in water
• D. Breaking a substance into smaller pieces

Answer: (A)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form of a substance but not its chemical composition, while a chemical change results in the formation of one or more new substances with different properties.
2. Analyze each option to determine if it indicates a chemical or physical change:
3. Formation of a gas typically indicates a chemical change because it suggests a new substance is being produced, often seen in reactions like decomposition or acid-base reactions.
4. Change in state from solid to liquid is a physical change because the substance's chemical identity remains the same; only its physical form changes.
5. Dissolving sugar in water is a physical change since sugar molecules disperse in water but do not chemically react or form new substances.
6. Breaking a substance into smaller pieces is a physical change because it only changes the size or shape, not the chemical composition.