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KS4 Chemistry Useful Oil.

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Presentation on theme: "KS4 Chemistry Useful Oil."— Presentation transcript:

1 KS4 Chemistry Useful Oil

2 Fractional distillation
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities

3 Hydrocarbons are molecules that contain carbon and hydrogen only.
Crude oil Crude oil is a mixture. It contains hundreds of different compounds. Some are small but most are large. Nearly all of these compounds contain carbon and hydrogen only. They are called hydrocarbons. Hydrocarbons are molecules that contain carbon and hydrogen only.

4 An oil rig Crude oil is often located underneath the sea bed.
Oil rigs or drilling platforms are used to drill through the sea bed to obtain the oil. The Columbus drilling rig. Image © BP

5 Hydrocarbons 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. Small molecules Big molecules Medium molecules

6 The importance of oil These hydrocarbons are vital to our way of life.
We use them as highly portable fuels for many forms of transport. We also use them as raw materials from which a huge range of useful everyday substances are made. Image © BP

7 Making oil useful 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.

8 An oil refinery Crude oil is separated into useful fractions in an oil refinery The Grangemouth Refinery, formerly owned by BP. Image © BP

9 Fractional distillation
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities

10 Fractional distillation
cool hot Crude oil is split into fractions containing similar sized molecules using fractional distillation. The oil is heated until it vaporises. It then passes up a tall tower that is hot at the bottom but cool at the top. As the vapour passes up this tower the molecules cool and condense back to liquid.

11 Fractions and boiling points
cool hot Copy the column and arrange the fractions in the right order next to the arrows. Fuel gas Petroleum Fraction Boiling Range (oC) Kerosine Diesel 220 – 275 Petrol Bitumen >350 Fuel gas Below 40 Lubricating oil Kerosine Diesel Lub. Oil Bitumen

12 How fractional distillation works

13 Fractional distillation
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities

14 The boiling point of hydrocarbons
We have already said that, in general, the bigger the molecule the higher the boiling point. No. Carbon atoms  B.Pt (oC)

15 Boiling point and fraction size
Here are the boiling ranges of some fractions obtained from distillation of petroleum. Using the previous graph, estimate the size range of the molecules present in each fraction. Fraction Boiling Range (oC) Number of carbons Fuel gas Below 40 Petrol Kerosine Diesel 1-5 5-10 9-14 13-17

16 Flammability of hydrocarbons
When hydrocarbons burn they are reacting with oxygen in the air. In general, the smaller the molecule the better it will mix and then react with the air.

17 Flash points Substance Flash Point Kerosine <23 Petrol 85 - 150
Flash points are (roughly) the temperature below which you cannot ignite the substance. Here is some flash points data for oil fractions. Link the molecule to the flash point. Substance Flash Point Kerosine <23 Petrol Fuel Oil

18 Viscosity of hydrocarbons
When we pour a liquid the molecules have to pass each other. The easier they do this, the runnier the liquid is. The molecules in fuel oil and bitumen may contain up to 400 carbon atoms in long chain structures. These chains easily become entangled reducing the runniness of the liquid and so those made up of big molecules tend to be viscous (treacly) not runny.

19 Viscosity of hydrocarbons
In contrast, small molecules are more spherical and tend not to get tangled. They are therefore likely to have a low viscosity (be runny). Bigger molecules Higher viscosity “Treacly” Smaller molecules Lower viscosity “Runny”

20 Matching hydrocarbons to their viscosity
Here are the viscosities of 5 hydrocarbons. The higher the value the less runny the hydrocarbon is. Draw arrows joining the hydrocarbon with the appropriate value. Hydrocarbon Viscosity (cP) Pentane - C5H12 0.40 Hexane - C6H12 0.52 Heptane - C7H16 0.24 Octane - C8H18 0.92 Decane - C10H22 0.70

21 Colour of hydrocarbons
Small hydrocarbon molecules are gases or transparent liquids. As the molecules get larger the colour becomes increasingly yellow through to the brown/black colour of bitumen used on roads and roof repairs. Increasing size of molecules 

22 Composition of fractions
We already know that each petroleum fraction consist of hydrocarbon molecules falling within a particular size range. The proportions of the different hydrocarbons present in oil can vary greatly across the world. It is therefore not surprising that the exact nature of the fractions collected will vary both in amount and detailed composition. Nonetheless most crude oil will give rise to some quantity of each type of fraction.

23 Viscosity of different crude oil
Using viscosity data for crude oil from different areas of the world, arrange the oils putting those with the smallest molecules first. Crude Order Viscosity (cSt) Saudi Arabia 47.7 UK (Brent) 6.13 Norway (Gulifaks) 16.5 Alaskan 31.5 Malaysian 3.43 5 2 3 4 1

24 Fractional distillation
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities

25 Uses of different fractions
Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas Fuel gas Petrol / gasoline Fuel for cars and motorcycles, also used to make chemicals. Naphtha Used to make chemicals. Paraffin / kerosine Fuel for greenhouse heaters and jet engines, manufacture of chemicals. Diesel fuel Fuel for lorries, trains. Fuel and lubricating oil Fuel for the heating systems of large buildings, fuel for ships, lubricating oil. Bitumen Roofing, and road surfaces.

26 Burning hydrocarbons The apparatus below is used to test the products of combustion of a hydrocarbon. Suction pump ice- water Lime water Candle wax is the hydrocarbon here Liquid collected can be tested with anhydrous cobalt chloride paper (bluepink). any hydrocarbon + oxygen  water + carbon dioxide

27 Fractional distillation
Contents Useful Oil Crude oil Fractional distillation Physical properties of fractions Uses of fractions Summary activities

28 Glossary combustion – A rapid reaction between a substance and oxygen that produces heat and light energy. crude oil – A naturally-occurring mixture of hydrocarbons and other substances. flammable – A substance that easily catches fire and burns rapidly. fractional distillation – The process used to separate crude oil into different fractions. hydrocarbon – A molecule containing only hydrogen and carbon. viscosity – A measure of how easily a liquid flows.

29 Anagrams

30 Multiple-choice quiz


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