P2 7 Organic chem (crude oil)

• fossil fuel formed over millions of years • biomass (mainly dead plankton) falls to sea bed, covered in layers of mud • mud turns into rock and dead organisms decay forming oil

• a mixture of many different compounds • mostly hydrocarbons- most found in crude oil are alkanes

C(n) H(2n+2)

CH4 methane C2H6 ethane C3H8 propane C4H10 butane

• crude oil vaporised (heated) so most alkane molecules turn into a gas • gas put in the bottom of a fractionating column where it is hottest • (as it is gas) they rise up the column and start to cool, once an alkane reaches its boiling point it condenses into a liquid and is collected -> crude oil molecules with extremely high boiling points will not vaporise, so are collected at the bottom of the column as a thick/sticky liquid -> long-chain hydrocarbons have higher boiling points so condense quicker+ will be collected near the bottom of the column

gets cooler as you move up the column (oil begins as a gas and condenses as a liquid)

• bitumen (unvaporised molecules remain as liquid, thick/sticky mixture) - tar for roads/roofs • fuel oil - ships • diesel oil - trucks/lorries • kerosene - plane fuel • petrol - cars • LPG (gas- doesn’t condense) - liquified for fuel or burned for domestic heating/cooking (methane/ethane..)

volatility- how easily a liquid vaporises volatile- a chemical that vaporises easily (so also easily flammable)

short - low as they are volatile (collected at top of column) long - high (collected at bottom of column)

short - high (as they are volatile) long - low

viscosity - how easily a liquid flows (how thick it is) viscous - a chemical that doesn’t flow easily, gloopy/thick

short - low, runny long - high (viscous), thick

CnH2n+2 + O2 -> CO2 + H2O hydrocarbon + oxygen -> carbon dioxide + water

• used for fuels • shorter-chain hydrocarbon molecules are best as they are more flammable so require less energy • hydrocarbons are oxidised during combustion -> produces carbon dioxide + water + ENERGY released

hydrocarbon + oxygen -> carbon monoxide OR carbon (soot) + water

• long-chain hydrocarbons are broken down into smaller-chain molecules -> smaller molecules are more useful for fuels as they are more flammable • also produces alkenes which are used to make polymers (plastic)

long-chain alkane -> shorter-chain alkane + alkene

(also hydrocarbons) more reactive than alkanes as they contain a double carbon bond (C=C) -> used to make polymers (plastics)

bromine water changes from orange-brown to colourless for a positive result -> alkanes don’t react with bromine water

• used to crack long-chain alkanes • produces moderate-chain alkanes used for fuels • requires a lower temperature • uses a catalyst (silica, SiO2) in powder form, increases SA to speed up the breakdown

• used to crack moderate-chain alkanes • produces short-chain alkanes used for petrochemicals • requires a higher temperature • also produces alkenes used for polymers (plastics)