Crude Oil

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  • Crude Oil
    • Cracking
      • Cracking means splitting up long-chain hydrocarbons
      • Cracking is a thermal decomposition reaction - breaking molecules down by heating them.
      • The first step is to heat the long-chain hydrocarbon to vaporise it (turn it to a gas)
        • Then the vapour is passed over a powdered catalyst at a temperature of about 400 degrees C - 700 degrees C.
        • Aluminium Oxide is the catalyst used.
        • The long-chain molecules split apart or 'crack' on the surface of the specks of catalyst.
      • Most of the products of cracking are alkanes and unsaturated hydrocarbons called alkenes.
      • Cracking also produces substances like ethene which  are needed for making plastic.
    • Crude oil is a mixture of hydrocarbons.
    • Crude oil is a mixture of many different compounds most of which are hydrocarbon molecules.
    • Hydrocarbons are basically fuels such as diesel and petrol. They're made of just carbon and hydrogen.
    • There are no chemical bonds between the different parts of  a mixture, so the different hydrocarbon molecules in crude oil are not chemically bonded to one another.
    • The different parts of crude oil can be separated using fractional distillation.
    • Crude oil is mostly alkanes
      • The first four alkanes are methane (natural gas), ethane, propane and butane.
        • Alkanes have a general formula  Cn H2n+2.
        • So if an alkane has 5 carbons, it's got to have (2x5)+2=12 hydrogens.
    • Properties of Crude Oil
      • The shorter the molecules the more runny the hydrocarbon is  (less viscous) ((gloopy)) it is.
      • Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms.
        • alkenes and Ethanol
          • Alkenes have a double c=c bond
          • These are known as UNSATURATED.
          • The first two alkenes are ethene and propene
            • all alkenes have the general formula CnH2n - they have twice as many hydrogens as carbons.
            • You can test for an alkene by adding the substance to bromine water. An ALKENE will DECOLOURISE the bromine water, turning it from orange to colourless. this is because the double bond opens up and forms a bond with the bromine water.
            • ETHENE can be reacted with STEAM to produce ETHANOL
              • Ethanol can also be produced from renewable resources.
      • The shorter the molecules, the more volatile they are. That means that they turn into a gas at a lower temperature. So, the shorter molecules, the lower the temperature at which that fractionvaporises or condenses - and the lower its boiling point.
        • Also the shorter the molecules, the more flammable the hydrocarbon is.
      • The volatility helps decide what the fraction is used for. The refinery gas fraction has the shortest molecules, so it has the lowest boiling point - it's actually gas at room temperature.
        • The petrol fraction has longer molecules, so it has a higher boiling point.
        • The viscosity also helps decide how the hydrocarbons are used. The really gloopy viscous hydrocarbons are used for lubricating engine parts.
          • Using crude oil  as a fuel.
            • Crude oil fractions burn cleanly so they make good fuels.



Amazing mindmap, thank you ;)

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