Which of the following is a sign that a chemical change might have occurred?

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

Answer: (D)

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 option to determine if it represents a physical or chemical change: Breaking a substance into smaller pieces is a physical change because the substance's composition remains the same.
3. Dissolving sugar in water is also a physical change because the sugar molecules disperse but do not chemically react or form new substances.
4. A change in state from solid to liquid (melting) is a physical change since the substance's chemical identity does not change.
5. Formation of a gas or bubbles indicates a chemical change because it suggests a new substance is being produced, often as a product of a chemical reaction.