- The diamond should be able to scratch a finger nail. A diamond has a hardness of 10, while a finger nail has a hardness of 2.5–3. Since the diamond is much harder, it can easily scratch the nail.
- Topaz and steel can scratch glass. Glass has a hardness of 5.5–6.5. Topaz has a hardness of 8, and steel has a hardness of 6–7, both of which are harder than glass.
- A copper penny should be able to scratch glass. Copper has a hardness of 3, which is softer than glass (5.5–6.5), so it cannot scratch glass. The correct answer is that a copper penny cannot scratch glass.
- A finger nail should not be able to scratch glass. Glass has a hardness of 5.5–6.5, while a finger nail has a hardness of 2.5–3. Since the nail is softer than glass, it cannot scratch it.
- To test chalk, you could use a fingernail or copper penny. Chalk is made of soft limestone and has a hardness of about 2–3. It should be scratched by a fingernail (hardness 2.5–3) and possibly by copper (hardness 3). Testing with these materials would confirm its softness.
Parent Tip: Review the logic above to help your child master the concept of mineral worksheet.
