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Carbon

Graphite

Graphite is a soft, shiny, dark gray or black, greasy-feeling mineral that is found in large masses throughout the world, including the United States, Brazil, England, western Europe, Siberia, and Sri Lanka. It is a good conductor of electricity and resists temperatures up to about 6,332°F (3,500°C), which makes it useful as brushes (conductors that slide along rotating parts) in electric motors and generators, and as electrodes in high-temperature electrolysiscells. Because of its slipperiness, it is used as a lubricant. For example, powdered graphite is used to lubricate locks, where oil might "gum up the works." The "lead" in pencils is actually a mixture of graphite, clay, and wax. It is called "lead" because the metallic element lead (Pb) leaves gray marks on paper and was used for writing in ancient times. When graphite-based pencils came into use, they were called "lead pencils."

The reason for graphite's slipperiness is its unusual crystalline structure. It consists of a stack of one-atom-thick sheets of carbon atoms, bonded tightly together into a hexagonal pattern in each sheet, but with only very weak attractions—much weaker than actual chemical bonds—holding the sheets together.

The sheets of carbon atoms can therefore slide easily over one another; graphite is slippery in the same way as layers of wet leaves on a sidewalk.


Additional topics

Science EncyclopediaScience & Philosophy: Calcium Sulfate to Categorical imperativeCarbon - How Carbon Is Found, Graphite, Diamond, The Chemistry Of Carbon, Why Carbon Is Special - Classes of carbon compounds