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

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

Answer: (D)

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:
3. 1. Change in state from solid to liquid (melting) is a physical change because the substance's chemical identity remains the same.
4. 2. Dissolving sugar in water is a physical change because sugar molecules disperse but do not chemically react or form new substances.
5. 3. Breaking a glass into pieces is a physical change because the glass is only physically broken, not chemically altered.
6. 4. Formation of a gas typically indicates a chemical change because it often results from a chemical reaction producing a new substance in the gaseous state.