Which of the following is the best way to determine if a chemical change has taken place?

• A. Detection of a change in physical state, such as melting or boiling
• B. Observation of the formation of a new substance with different properties
• C. Observation of a change in size or shape of the material
• D. Measurement of a change in temperature without any other evidence

Answer: (B)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: Physical changes affect the form of a substance but not its chemical composition, while chemical changes result in the formation of one or more new substances with different properties.
2. Recognize that changes in physical state (like melting or boiling) and changes in size or shape are examples of physical changes, as the substance's identity remains the same.
3. Note that a change in temperature alone does not necessarily indicate a chemical change, as physical processes can also involve temperature changes.
4. Identify that the key indicator of a chemical change is the formation of a new substance with properties different from the original material.
5. Therefore, the best way to determine if a chemical change has taken place is to observe the formation of a new substance with different properties.