Which of the following physical properties can be used to help identify a metal that is a pure substance?

• A. Melting point
• B. Color in solution
• C. Ability to conduct electricity
• D. Reactivity with acid

Answer: (A)

Verified step by step guidance

1. Understand that physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical identity.
2. Review each option to determine if it is a physical property or a chemical property: Melting point is a physical property because it involves a phase change without altering the substance's composition.
3. Color in solution is not a reliable physical property for identifying a pure metal because metals typically do not dissolve to form colored solutions; this often involves chemical changes or impurities.
4. Ability to conduct electricity is a physical property common to many metals, but it is not unique enough to identify a specific pure metal since many metals conduct electricity.
5. Reactivity with acid is a chemical property because it involves a chemical reaction that changes the substance's composition, so it cannot be used as a physical property to identify a pure metal.