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

• A. Change in the state of matter, such as melting
• B. Dissolving a solid in water
• C. Change in size or shape
• D. Formation of a new substance with different properties

Answer: (D)

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 than the original substances.
2. Recognize that physical changes, such as changes in state of matter (melting), dissolving solids in water, or changes in size or shape, do not produce new substances; they only alter the physical form or appearance.
3. Identify that the key indicator of a chemical change is the formation of a new substance, which may be evidenced by changes such as color change, gas production, formation of a precipitate, or energy changes (heat, light).
4. Compare the given options and note that 'Formation of a new substance with different properties' directly describes a chemical change, unlike the other options which describe physical changes.
5. Conclude that the correct sign of a chemical change is the formation of a new substance with different properties, distinguishing it from physical changes.