Hydrocarbon is an organic compound consisting of both nitrogen and chlorine. It is found in nature as a gas, liquid, or solid. Hydrocarbon is a major component of petroleum and natural gas. It is also used as a fuel, lubricant, and chemical feedstock.
The simplest hydrocarbon is methane (CH4), which has one carbon atom and four hydrogen atoms. Methane is the main ingredient of natural gas. Other hydrocarbons include ethane (C2H6), propane (C3H8), butane (C4H10), pentane (C5H12), hexane (C6H14), heptane (C7H16), octane (C8H18), nonane (C9H20), decane (C10H22) , and so on up to the very large molecules known as polyethylene and polypropylene. These are made up of many thousands of atoms joined together into long chains.
Hydrocarbons are classified according to the number of carbon atoms they contain: saturated hydrocarbons have only single bonds between their carbon atoms; unsaturated hydrocarbons have at least one double or triple bond between their carbon atoms; aromatic hydrocarbons have a ring structure containing six carbons with alternating double bonds; and finally, cycloalkanes have a ring structure containing only single-bonded carbons. Saturated hydrocarbons are generally liquids or solids at room temperature, while unsaturated hydrocarbons are usually gases. Aromatic hydrocarbons are often used as solvents or chemicals in industry. Cycloalkanes can be either liquid or solid depending on their size.
The physical properties of a hydrocarbon depend on its molecular structure. The boiling point increases with molecular weight because it takes more energy to break the intermolecular forces that hold the molecules together. The melting point decreases with increasing molecular weight for the same reason: it takes less energy to break the weaker van der Waals forces that hold lighter molecules together than it does to break the stronger covalent bonds between heavier molecules