Which of the following is a common indicator that a chemical change has taken place during a chemical reaction?

• A. Dissolving a solid in water
• B. Breaking a glass into smaller pieces
• C. Formation of a gas (bubbling or fizzing)
• D. Change in physical state from solid to liquid

Answer: (C)

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 represents a physical or chemical change: Dissolving a solid in water is usually a physical change because the substance's chemical identity remains the same.
3. Breaking a glass into smaller pieces is a physical change because the glass's chemical composition does not change, only its shape and size.
4. Formation of a gas (bubbling or fizzing) is a common indicator of a chemical change because it shows that a new substance (gas) is being produced during the reaction.
5. Change in physical state from solid to liquid is a physical change since it involves a change in state without altering the chemical identity of the substance.