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

• A. Formation of a gas
• B. Dissolving sugar in water
• C. Change in size or shape
• D. Change in state from solid to liquid

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. - Dissolving sugar in water is a physical change because the sugar molecules disperse but do not chemically react or form new substances.
4. - Change in size or shape is a physical change since it only alters the physical dimensions without changing the substance's identity.
5. - Change in state from solid to liquid is a physical change involving a phase transition without altering the chemical composition.
6. - Formation of a gas typically indicates a chemical change because it often results from a chemical reaction producing a new gaseous substance.