C1.4 Crude oil and fuels

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  • Crude oil
    • Formation
      • Fossil fuel
        • This means that this source of fuel isn't sustainable because the fossils require millions of years to form and the supply of crude oil (and other fossil fuels) is running out.
      • Dead sea animals sunk to the bottom of the sea millions of years ago.
        • Their bodies didn't decay due to a lack of oxygen.
          • This meant that bacteria wasn't able to decompose the bodies so they remained there.
            • Under the high temperatures and pressure, the fossils were compacted together and formed the fossil fuel.
    • Separating
      • Fractional distilation
        • Separates the hydrocarbons into fractions, with similar boiling points and similar number of carbon atoms
        • The oil is first evaporated and then condenses at different temperature.
        • The fractions at the top of the fractional distillation have a lower boiling point, smaller chained molecules (more useful) and are more volatile.
        • The fractions at the bottom of the column have higher boiling points, larger chained molecules and aren't volatile.
      • Cracking
        • The process by which the fractions from the fractional distillation are broken down further to make smaller molecules
          • E.G ethene
            • Alkenes have a general formula of: CnH2n
            • Alkenes always have a double bond
          • E.G polymers
        • They are broken down because the smaller molecules are more useful.
        • 1. The hydrocarbons are heated
          • 2. The vapours are passed over a hot catalyst
          • OR 2. Mixed with the steam and heated to a very high temperature (so thermal decomposition reaction can occur)
    • What is crude oil?
      • A hydrocarbon (compound composed of hydrogen and carbon ONLY)
      • Saturated compounds (alkanes)
        • Which have a general formula of: CnH2n+2
      • Crude oil is a mixture of a very large number of compounds
    • Combustion
      • When the oil is burned, C02 is released into the atmosphere which is a green house gas. This adds to the green house effect.
      • The combustion of hydrocarbon fuels releases energy.
      • During combustion the hydrogen and carbon in the fuels are oxidised.

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