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neurologyYou need to know

• Crude oil is formed from the remains of ancient marine organisms, mainly plankton, buried in sediment and changed by heat and pressure over millions of years in the absence of enough oxygen for decay.
• Crude oil is a finite fossil fuel because it forms extremely slowly and is being used much faster than it is naturally made.
• Crude oil is a mixture of many different hydrocarbons, which are compounds made only from hydrogen and carbon atoms.
• Most hydrocarbons in crude oil are alkanes, which are saturated hydrocarbons containing only single covalent bonds between carbon atoms.
• The general formula of an alkane is `C_nH_{2n+2}`.
• The first four alkanes are methane `CH_4`, ethane `C_2H_6`, propane `C_3H_8`, and butane `C_4H_{10}`.
• As alkane molecules get larger, their boiling points increase because stronger intermolecular forces require more energy to overcome.
• As alkane molecules get larger, they become more viscous, less volatile, and less flammable.
• Fractional distillation separates crude oil into fractions because different hydrocarbons have different boiling points.
• In fractional distillation, crude oil is vaporised, the column is hot at the bottom and cooler at the top, and hydrocarbons condense at the level where the temperature is below their boiling point.
• Small hydrocarbon molecules condense near the top of a fractionating column, while large hydrocarbon molecules condense lower down.
• Useful crude oil fractions include refinery gases for bottled gas, petrol for cars, kerosene for aircraft fuel, diesel oil for diesel vehicles, fuel oil for ships and power stations, and bitumen for road surfaces and roofs.
• Complete combustion happens when a hydrocarbon burns in a plentiful supply of oxygen to produce carbon dioxide and water.
• Incomplete combustion happens when a hydrocarbon burns in a limited supply of oxygen and produces water plus carbon monoxide and/or carbon particulates.
• A balanced equation for complete combustion of methane is `CH_4 + 2O_2 -> CO_2 + 2H_2O`.
• Balanced equations for incomplete combustion of methane include `2CH_4 + 3O_2 -> 2CO + 4H_2O` and `CH_4 + O_2 -> C + 2H_2O`.
• Carbon dioxide turns limewater milky, and water turns anhydrous copper sulfate from white to blue or cobalt chloride paper from blue to pink.
• Cracking is the thermal decomposition of long-chain hydrocarbons into shorter, more useful alkanes and alkenes.
• Catalytic cracking uses a hot vaporised hydrocarbon passed over a hot catalyst such as aluminium oxide or silica.
• Steam cracking uses a hot vaporised hydrocarbon mixed with steam and heated to a very high temperature without a catalyst.

• Draw displayed formulae for methane, ethane, propane and butane, showing the correct number of carbon and hydrogen atoms and only single covalent bonds.
• Name alkanes from their chemical or displayed formulae by counting the carbon atoms and using methane, ethane, propane or butane correctly.
• Predict how boiling point, viscosity, volatility and flammability change as alkane chain length increases, using intermolecular forces in the explanation.
• Explain fractional distillation of crude oil by linking vaporisation, the temperature gradient in the column, condensation and different boiling points.
• Write balanced word and symbol equations for complete and incomplete combustion of hydrocarbons, ensuring atoms are conserved on both sides.
• Test for the products of complete combustion by using limewater for carbon dioxide and anhydrous copper sulfate or cobalt chloride paper for water.
• Write a balanced cracking equation in which one long-chain alkane forms shorter molecules, including at least one alkene product.
• Test for unsaturation by adding bromine water and identifying a positive result as a colour change from orange to colourless.
• Draw and name ethene, propene and butene, showing one carbon-carbon double bond and the correct chemical formula for each alkene.