Which of the following is a physical property?

• A. A characteristic of a pure substance that can be observed without changing it into another substance
• B. A property that only appears after a chemical reaction
• C. A change in a substance that alters its identity
• D. A change that does not involve the substance's identity

Answer: (A)

Understanding physical properties means you can describe a substance by what you observe or measure without changing its composition. A physical property is something like color, melting point, density, or hardness—observed without turning the substance into something else. The statement given matches this idea: it describes a characteristic that you can observe without changing the substance, which is exactly what a physical property is. The other phrases refer to aspects that require a chemical reaction or a change in the substance’s identity, which are not physical properties.