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Crude Oil

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  1. Noadswood Science, 2011 Crude Oil

  2. Crude Oil • To understand what crude oil is and how it can be used

  3. Crude Oil • How is oil formed and how is it found in its ‘natural’ state? • Fossil fuels formed millions of years ago from the remains of living things (coal from plants and natural gas and oil from sea creatures) - they were gradually buried by layers of rock which stopped them rotting…

  4. Crude Oil • The buried remains were put under pressure and chemical reactions heated them up, gradually changing into fossil fuels

  5. Crude Oil • Some oil and natural gas was covered by cap rock which is impermeable (not letting them through) • They can be removed from the ground by drilling through the rock

  6. Fossil Fuels

  7. Coal

  8. Oil & Gas

  9. Crude Oil • Crude oil is a mixture of compounds called hydrocarbons – they only contain hydrogen and carbon atoms, joined together by chemical bonds • There are different types of hydrocarbon, but most of the ones in crude oil are alkanes…

  10. Alkanes • The alkanes are a family of hydrocarbons that share the same general formula: - CnH2n+2 • The general formula means that the number of hydrogen atoms in an alkane is double the number of carbon atoms, plus two • E.g. methane is CH4 and ethane is C2H6 • Alkane molecules can be represented by displayed formulae in which each atom is shown as its symbol (C or H) and the chemical bonds between them by a straight line…

  11. Alkanes *The bonds are not really at 90o – as shown by the ball and stick model

  12. Alkanes • As the alkane chain increases in length the properties change… • Longer chains mean: - Less ability to flow (more viscous) Less flammable Less volatile Increased boiling points Increasing chain length

  13. Alkanes • Alkanes are saturated hydrocarbons – this means that their carbon atoms are joined to each other by single bonds • This makes them relatively un-reactive, apart from their reaction with oxygen in the air during combustion (they do burn well)!

  14. Alkanes • Hydrocarbons have different boiling points, and can be either solid, liquid or gas at room temperature: - • Small hydrocarbons with only a few carbon atoms have low boiling points and are gases • Hydrocarbons with between 5 and 12 carbon atoms have medium boiling points and are usually liquids • Large hydrocarbons with many carbon atoms have high boiling points and are solids

  15. Crude Oil • Why is crude oil so important? • Some of the 21st century’s most important chemistry involves chemicals that are made from crude oil – they are used for fuels in cars; warming of homes; making electricity etc… • When oil prices rise it affects us all – countries that produce crude oil can have an affect on the world economy by the price charged for oil • Crude oil originates as a dark, smelly liquid which is a mixture of lots of different chemical compounds – it is not much use straight out of the ground (there are too many substances in it, all with different boiling points). As such it needs to be refined…

  16. Parts • Although we can get useful substances from oil, crude oil itself has no uses • In order to make crude oil into useful substances we first have to separate the mixture into molecules of similar size – this is done in an oil refinery…

  17. Parts • Crude Crude oil is a mixture of different sized hydrocarbons – the exact composition depends upon where the oil comes from but typically it contains a lot of big molecules

  18. Distillation • Distillation is a process that can be used to separate a pure liquid from a mixture of liquids – it works when the liquids have different boiling points

  19. Fractional Distillation • Fractional distillation differs from distillation only in that it separates a mixture into a number of different parts, called fractions • A tall column is fitted above the mixture, with several condensers coming off at different heights • The column is hot at the bottom and cool at the top – substances with high boiling points condense at the bottom and substances with low boiling points condense at the top • Like distillation, fractional distillation works because the different substances in the mixture have different boiling points

  20. Fractional Distillation • Watch the demo of fractional distillation of crude oil…

  21. Fractional Distillation • Because they have different boiling points, the substances in crude oil can be separated using fractional distillation • The crude oil is evaporated and its vapours allowed to condense at different temperatures in the fractionating column – each fraction contains hydrocarbon molecules with a similar number of carbon atoms

  22. Fractional Distillation • Oil fractions – the gases condense at the top of the column, the liquids in the middle and the solids stay at the bottom… • The main fractions include refinery gases, gasoline (petrol), naphtha, kerosene, diesel oil, fuel oil, and a residue that contains bitumen • These fractions are mainly used as fuels, although they do have other uses too • Hydrocarbons with small molecules make better fuels than hydrocarbons with large molecules because they are volatile, flow easily and are easily ignited

  23. Fraction Differences • Observe the differences in the fractions between their viscosity, flammability and volatility… Petrol Natural Gas Bitumen

  24. Fractional Distillation