Diamond is the hardest substance known on earth. Although diamonds found in nature are colorless and transparent, when combined with other elements its color can range from pastels to black. Diamond is a poor conductor of heat and electricity. Until 1955 the only sources of diamond were found in deposits of volcanic origin. Since then scientists have found ways to make diamond from graphite and other synthetic materials. Diamonds of true gem quality are not made in this way .
Graphite is another form of carbon. It occurs as a mineral in nature, but it can be made artificially from amorphous carbon. One of the main uses for graphite is for its lubricating qualities. Another is for the "lead" in pencils.
Graphite is used as a heat resistant material and an electricity conductor.
Amorphous carbon is a deep black powder that occurs in nature as a component of coal. It may be obtained artificially from almost any organic substance by heating the substance to very high temperatures without air. Using this method, coke is produced from coal, and charcoal is produced from wood. Amorphous carbon is the most reactive form of carbon. Because amorphous carbon burns easily in air, it is used as a combustion fuel.
Carbon dioxide is commonly found as a gas and is never a liquid. It sublimes to a solid known as 'dry ice' which is used as a substitute for normal ice as it is a lot colder and doesn't melt.
However this natural balance is disrupted by human activity. People of the world are putting more than 5.5 billion tons of CO2 into the