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neurologyYou need to know

• Crude oil is formed over millions of years from the buried remains of tiny marine plants and animals that were heated and compressed in the absence of air.
• Crude oil is a finite fossil fuel because it forms far more slowly than humans use it.
• Crude oil is a mixture of hydrocarbons, which are compounds made only from carbon and hydrogen 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 CH₄, ethane C₂H₆, propane C₃H₈ and butane C₄H₁₀.
• As alkane chain length increases, boiling point increases because larger molecules have stronger intermolecular forces.
• As alkane chain length increases, viscosity increases, volatility decreases and flammability decreases.
• Fractional distillation separates crude oil because different hydrocarbons have different boiling points.
• In fractional distillation, crude oil is vaporised and the vapours condense at different heights in a fractionating column, with high boiling point fractions condensing near the hot bottom and low boiling point fractions condensing near the cool top.
• The main fractions of crude oil include refinery gases for heating and cooking, petrol for cars, kerosene for aircraft, diesel for vehicles, fuel oil for ships and power stations, and bitumen for road surfaces and roofs.
• Complete combustion happens when a hydrocarbon burns in plenty of oxygen to produce carbon dioxide and water.
• Incomplete combustion happens when a hydrocarbon burns in a limited supply of oxygen to produce water and carbon monoxide and/or carbon particulates.
• Carbon monoxide is a toxic gas because it reduces the ability of blood to transport oxygen.
• Carbon dioxide from complete combustion can be tested with limewater, which turns milky or cloudy when carbon dioxide is present.
• Water from combustion can be tested with anhydrous copper sulfate, which turns from white to blue, or cobalt chloride paper, which turns 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 catalyst, such as aluminium oxide or silica, to break large molecules into smaller molecules.
• Steam cracking uses very high temperature steam to break large hydrocarbon molecules into smaller molecules.
• Alkenes are unsaturated hydrocarbons that contain a carbon-carbon double bond, and the first three alkenes are ethene C₂H₄, propene C₃H₆ and butene C₄H₈.

• Draw displayed formulae for alkanes by showing all atoms and single covalent bonds, ensuring each carbon atom forms four bonds and each hydrogen atom forms one bond.
• Name straight-chain alkanes and alkenes from their number of carbon atoms using the correct prefixes: meth-, eth-, prop- and but-.
• Explain trends in alkane properties by linking increasing chain length to stronger intermolecular forces and therefore higher boiling point, lower volatility, higher viscosity and lower flammability.
• Describe fractional distillation using the sequence: vaporise crude oil, pass vapours into a fractionating column, cool and condense fractions at different heights according to boiling point.
• Write balanced symbol equations for complete combustion of hydrocarbons, ensuring carbon atoms form carbon dioxide and hydrogen atoms form water.
• Write balanced symbol equations for incomplete combustion of hydrocarbons, using carbon monoxide or carbon as a product when oxygen is limited.
• Test for products of complete combustion by passing carbon dioxide through limewater and testing condensed water with anhydrous copper sulfate or cobalt chloride paper.
• Calculate reacting masses for combustion reactions by converting mass to moles, using the balanced equation ratio, and converting moles back to mass.
• Write a balanced cracking equation by ensuring the total number of carbon and hydrogen atoms is the same on both sides and that at least one product is an alkene.
• Test for unsaturation by adding bromine water, where an alkene turns orange bromine water colourless but an alkane does not react.