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'Petroleum.'Crude oil is a mixture of different hydrocarbons and can be broken down into separate fractions by a process called fractional distillation.

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'Petroleum.' Petroleum is also known as crude oil. Petroleum naturally seeps to the Earth's surface along fault lines and cracks in rocks, where it gathers in pools as tar, asphalt or bitumen. From this property it gets its name: the Latin petra, meaning 'rock' and oleum, meaning 'oil', 'rock oil'. Crude oil deposits are found all over the world. Petroleum in a solid form is called asphalt. In liquid form petroleum is called crude oil and in a gaseous form is called natural gas. Petroleum is a mixture of organic compounds containing just two elements: carbon and hydrogen and is the most important natural source of fuel, it is also the source of the raw materials used to make detergents, plastics, paints, anti-freeze, synthetic rubber and medicines. Crude oil is a mixture of different hydrocarbons and can be broken down into separate fractions by a process called fractional distillation. The majority of compounds in crude oil are straight alkanes, but the mixture also contains cycloalkanes and arenas. ...read more.


o Petrol (gasoline) - used for petrol. o Naphtha - used for petrochemicals. o Kerosine (paraffin) - used for jet fuel and petrochemicals. o Gas oil (diesel) - used for central heating fuel and petrochemicals. o Mineral oil (lubricating oil) - used for lubricating oil and petrochemicals. o Fuel oil - used for fuel for ships and power stations. o Wax, grease - used for candles, grease for bearings and polish. o Bitumen - used for roofing and road surfacing. The most useful oil fractions tend to contain the shorter chain hydrocarbons. Petrol is very useful; its chain length can be from C6 to C10. To meet the demand for petrol, larger chains need to be broken down into smaller chains. A process called cracking does this. Cracking is the chemical splitting of long chain alkanes into shorter chain hydrocarbons. Cracking involves a free radical reaction in which carbon-carbon and carbon-hydrogen bonds are broken. ...read more.


Long chained alkane molecules fit into the pores and when this mixture is exposed to a slight pressure and temperature of about 450?C, cracking occurs. Catalytic cracking is a lot cheaper and produces more branched chain molecules than thermal cracking. Branched hydrocarbons burn more easily and so are more useful as fuels. This is the main method of producing petrol. Many fractions obtained from crude oil are used as fuels because they react exothermically when they burn in oxygen. When we use petrol in cars, kerosene in aircraft, fuel oil, heating oil, diesel and natural gas, we use the exothermic energy produced. But burning hydrocarbons also releases carbon dioxide, a greenhouse gas. Impurities present in crude oil can cause environmental problems, for example: crude oil contains sulphur, which after fractional distillation can be found in the petrol fraction. So when the petrol burns, sulphur also reacts with oxygen to form sulphur dioxide, which is released into the atmosphere with the exhaust gases. Sulphur dioxide reacts with water and oxygen in the atmosphere to form sulphuric acid, which can cause acid rain. Charlotte Nellist Chemistry Essay Page 1 ...read more.

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