hydrocarbons and crude oil

compounds that contain hydrogen and carbon atoms only.

complex mixture of hydrocarbons (mostly alkanes) and a finite resource that is found in the Earth’s crust

the remains of organisms that lived and died millions of years ago- mainly plankton

-fuels such as petrol, diesel, kerosene - solvents lubricants detergents

to separate crude oil into simpler, more useful mixtures

• heated crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top( temperature gradient) , • vapours from the oil rise through the column • vapours condense when they become cool enough liquids are led out of the column at different heights

• weak intermolecular forces so low boiling points • They do not condense, but leave the column as gases • flammable -less viscous

have stronger intermolecular forces, so they have high boiling points, so they condense back into liquids • They leave the column as hot liquid bitumen. • viscous • less flammable

fractions, they are only a part of the crude oil

at the top - liquified petroleum gas petrol- fuel for cars kerosene- fuel for aircraft diesel- for cars and trains heavy fuel oil - for ships and power stations bitumen- for roads and roofs

• exothermic • carbon dioxide and water are produced • the maximum amount of energy is given out

hydrocarbon+oxygen –> carbon dioxide+water

• happens when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced. Less energy is released than during complete combustion.

a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules

alkanes and alkenes

hexane (C6H14) = butane C4H10 + ethene C2H4

• heat long chain hydrocarbons to vaporise them • the vapour is then passed over a hot powdered zeolite (aluminium oxide) catalyst • the long chain molecules split apart on the surface of the specks of the catalyst THIS IS CATALYTIC CRACKING

• you can also crack hydrocarbons if you vaporise them, mix them with steam then heat them to a very high temperature

It helps to match the supply of fractions with the demand for them. It produces alkenes, which are useful as feedstock for the petrochemical industry. • Very often, fractional distillation of crude oil produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want. Smaller hydrocarbons are more useful as fuels than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand.