Which of the following is a sign of a chemical change?

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

Answer: (D)

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. Analyze each option to determine if it represents a chemical or physical change:
3. - Dissolving sugar in water is a physical change because sugar molecules disperse but do not chemically alter.
4. - Changing state from solid to liquid (melting) is a physical change because the substance's identity remains the same.
5. - Breaking a substance into smaller pieces is a physical change because it only changes the size, not the chemical composition.
6. - Formation of a gas usually indicates a chemical change because it often results from a reaction producing a new gaseous substance.