Which of the following is NOT listed as a physical property of materials?

• A. Optical properties
• B. Electrical conduction and insulation
• C. Toughness
• D. Thermal conduction and insulation

Answer: (C)

The main idea here is distinguishing physical properties from mechanical properties. Physical properties describe how a material interacts with energy sources like light, electricity, or heat. Optical properties show how light interacts with the material, electrical conduction/insulation describes how electricity moves or doesn’t move, and thermal conduction/insulation covers how heat transfers. Toughness, however, is about how a material behaves under mechanical stress—its ability to absorb energy and resist fracture—which makes it a mechanical property rather than a physical property. So toughness is not listed as a physical property.