Why Diamonds Have High Melting Points


With their strong molecular structure, diamonds have an extremely high melting point. Melting point is the temperature required to break the intermolecular bonds between molecules of a substance. This means the bonds such as carbon bonds and polar attractions between the individual molecules of a substance must be broken so the molecules can flow past each other in a liquid state.

The Structure of a Diamond

  • Understanding the chemistry of diamond requires a basic knowledge of the element of carbon. Diamonds are made up of repeating units of carbon atoms. The crystal structure of a diamond is a face-centered cubic structure. Each carbon atom joins four other carbon atoms. Based on the cubic form and its highly symmetrical arrangement of atoms, diamond crystals can develop into several different shapes, knows as "crystal habits."

The Hardness of a Diamond

  • By understanding the shape of diamonds, the hardness of the structure can be analyzed. Hardness can be defined by a mineral's resistance to being scratched. This process is hardly employed today by mineral collectors because it's not precise enough in gemology. To measure this hardness, the Moh's scale is used. The test for hardness is carried out using sharp instruments of various hardness applied to the lowest part of the gem and starting with the lowest hardness first, until scratch is made. Diamond has a hardness of 10 on the Mohs Scale.

Thermal Property of a Diamond

  • With its hardness and structure, diamonds have a remarkable property of unsurpassed thermal conductivity. In contrast to metals, in which heat is conducted by electrons, lattice vibrations are responsible for diamond's high thermal conductivity. Lattice vibration occurs among the atoms in a crystal which are not locked into a rigid pattern, oscillating around their average position. When a whole group does this in a synchronized way, it is called lattice vibration. With these properties, the internal bonding of atoms contribute massively to the ability of diamonds to withstand high temperature.

The Melting Point of Diamonds

  • Diamonds conduct heat very well --- five times better than the second best heat conducting element, silver. They have a melting point of up to 3,820 degrees Kelvin. As heat is given to diamond, the energy is transferred throughout the molecule and dispersed by the huge number of bonds. Once carbon bonds begin breaking due to the extremely high heat, the molecule begins to melt.

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