Which of the following physical properties is commonly used to help identify and classify materials?

• A. Reactivity with acids
• B. Ability to conduct electricity
• C. Color
• D. Density

Answer: (D)

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 the options given: Reactivity with acids is a chemical property because it involves a chemical change.
3. Ability to conduct electricity is a physical property, but it is not as commonly used as density for identifying materials.
4. Color is a physical property but can be subjective and less reliable for classification due to variations and impurities.
5. Density, defined as mass per unit volume (\[\text{Density} = \frac{\text{Mass}}{\text{Volume}}\]), is a consistent and measurable physical property widely used to identify and classify materials.