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

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

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 form or state of a substance without changing its identity.
2. Review each option to determine if it indicates a chemical or physical change:
3. - Formation of a gas often indicates a chemical reaction because new gaseous products are produced.
4. - Breaking a substance into smaller pieces is a physical change since the substance's identity remains the same.
5. - Dissolving sugar in water is a physical change because sugar molecules disperse but do not chemically change.
6. - Change in state from solid to liquid is a physical change involving only a phase transition, not a new substance.