Which of the following observations would indicate that a chemical change has occurred?

• A. Breaking a glass into smaller pieces
• B. Melting of ice into liquid water
• C. Formation of a gas when two solutions are mixed
• D. Dissolving sugar in water

Answer: (C)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: Physical changes affect the form of a substance but not its chemical composition, while chemical changes result in the formation of new substances with different properties.
2. Analyze each observation to determine if it involves a change in chemical composition or just a physical change:
3. Breaking a glass into smaller pieces is a physical change because the glass's chemical composition remains the same, only its shape and size change.
4. Melting of ice into liquid water is a physical change because it involves a phase change without altering the chemical identity of H\_2O.
5. Formation of a gas when two solutions are mixed indicates a chemical change because the production of a gas suggests new substances are being formed through a chemical reaction.