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

• A. Formation of a new substance with different properties
• B. Dissolving a solid in a liquid to form a solution
• C. Change in size or shape without altering composition
• D. Change in the state of matter, such as melting or boiling

Answer: (A)

Verified step by step guidance

1. Understand that a chemical change involves the formation of one or more new substances with different chemical properties and compositions compared to the original substances.
2. Recognize that physical changes, such as dissolving a solid in a liquid, changing size or shape, or changing the state of matter (melting, boiling), do not produce new substances but only alter physical properties.
3. Identify that the key indicator of a chemical change is the formation of a new substance with different properties, which may be evidenced by color change, gas production, precipitate formation, or energy change.
4. Compare each option given: dissolving a solid forms a solution but no new substance; changing size or shape is a physical change; changing state is also physical; only formation of a new substance indicates a chemical change.
5. Conclude that the correct sign of a chemical change is the formation of a new substance with different properties.