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

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

Answer: (B)

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 indicates a chemical change: Dissolving a solid in water is usually a physical change because the substance's chemical identity remains the same.
3. Consider changes in physical state, such as melting or boiling: These are physical changes because the substance changes form but not its chemical composition.
4. Evaluate changes in size or shape: These are physical changes as they do not alter the chemical identity of the substance.
5. Identify the formation of a new substance with different properties as the reliable indicator of a chemical change, since it implies a change in chemical composition and the creation of new substances.