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

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

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 given: dissolving a solid in water is usually a physical change because the substance's chemical identity remains the same, just dispersed in water.
3. Consider the change in state of matter, such as melting. This is a physical change because the substance changes phase but its chemical composition does not alter.
4. Look at the change in size or shape. This is also a physical change since it only affects the physical dimensions without changing the substance's chemical identity.
5. Recognize that the formation of a new substance with different properties is a definite indicator of a chemical change, as it implies a chemical reaction has occurred producing new chemical species.