Gary has a piece of diamond and a piece of graphite. He wants to test the hardness of these two minerals. When he rubs the diamond against the piece of graphite, the graphite gets scratched. When he rubs the piece of graphite against the diamond, the diamond does not get scratched. Which of these is true? A. The graphite is harder than the diamond. B. This test does not show which mineral is harder. C. The diamond is harder than the graphite. D. Both minerals have the same hardness.

C) The diamond is harder than graphite!

Option (C)

Explanation:

The hardness of any material depends upon the type of chemical bonds and the energy requires to break that bond. Diamond and graphite has covalent bonding between their carbon atoms.

Gary rubs the diamond the graphite piece is scratched because diamond has strong covalent bonding then graphite. The bond energy of diamond is much higher than graphite. Gary rubs the piece of graphite against diamond, diamond doesn't scratch because diamond is harder than graphite.

Thus, the correct answer is option (C).