CHEMISTRY - UNIT 10 
CARBON COMPOUNDS
Hydrocarbons 
Crude Oil 
Fractional Distillation of Crude Oil 
Cracking 
Dependence On Hydrocarbons 
The simplest of organic compounds
Only contain Hydrogen & Carbon Atoms
Alkanes 
Simplest type of hydrocarbon - have C-C single bonds
General formula CnH2n+2
A homologous series - group of organic compounds that react in similar way
Saturated compounds - each carbon atom forms 4 single covalent bonds
First 4 alkanes are methane, ethane, propane & butane
Combustion = hydrocarbon + oxygen --> carbon dioxide + water (+ energy)
Properties change as chain gets longer
The shorter the chain the more runny it is (less viscous) & the more volatile it is, has lower boiling point at which it vaporises or condenses & more flammable
Non-renewable fuel like coal, oil & gas as take so long to make - finite resource
= Fossil fuel from remains of plants & animals, mainly plankton
Crude oil is mixture of different hydrocarbons, mostly alkanes
The different compounds in crude oil are separated by fraction distillation
Process
2) Temperature gradient in the column - hot at bottom, cooler as go up
3) The longer hydrocarbons have high boiling points & condense back into liquids & drain out early on, when they're near the bottom
1) The oil is heated until most turned into gas - gases enter a fractionating column (& liquid drained off)
4) Shorter hydrocarbons have lower boiling points & condense & drain out much later on near to the top of the column where it's cooler
5) End up with the crude oil mixture separated out into different fractions with similar boiling points
Main source of hydrocarbons & feedstock for petrochemical industry
Each fraction is largely mixture of general formula CnH2n+2
Crude oil provides fuel for most modern transport - diesel, kerosene, heavy fuel oil & Liquid Petroleum Gas (LPG)
Petrochemical industry uses hydrocarbons from crude oil as feedstock to make new compounds for use in things like polymers, solvents, lubricants & detergents
Products from crude oil are organic compounds (contain carbon atoms).
Large variety of products because carbon atoms can bond together to form different groups called homologous series - similar compounds with many properties in common.
Means splitting up long-chain hydrocarbons by breaking molecules down by heating them
Short-chain hydrocarbons are flammable so good for fuels & in high demand
Long-chain hydrocarbons form thick gloopy liquids like tar which aren't all that useful
The longer alkane molecules produced from fractional distillation are turned into smaller ones by process called cracking
Cracking produces alkanes & another type of hydrocarbon called alkenes - useful as starting material for other compounds & can be used to make polymers