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© Boardworks Ltd 2003 KS4 Useful Products from Organic Sources ORGANIC CHEMISTRY
© Boardworks Ltd 2003 Crude oil mixtureCrude oil is a mixture. It contains hundreds of different compounds. Some are small but most are large. only.Nearly all of these compounds contain carbon and hydrogen only. They are called hydrocarbons. only Hydrocarbons are molecules that contain carbon and hydrogen only.
© Boardworks Ltd 2003 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.
© Boardworks Ltd 2003 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. oil refineryThis is done in an oil refinery. Making oil useful
© Boardworks Ltd 2003 What is crude oil? 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 Medium molecules Big molecules
© Boardworks Ltd 2003 Fractional Distillation fractional distillation.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. coolcool hothot
© Boardworks Ltd 2003 Copy the column and arrange the fractions in the right order next to the arrows. FractionBoiling Range ( o C) Kerosine150 - 240 Diesel220 – 275 Petrol40 - 175 Bitumen>350 Fuel gasBelow 40 Lubricating oil250-350 coolcool hothot Fuel gas Petroleum Kerosine Diesel Lub. Oil Bitumen Fractional Distillation
© Boardworks Ltd 2003 Fractional Distillation
© Boardworks Ltd 2003 The boiling points of molecules We have already said that, in general, the bigger the molecule the higher the boiling point. No. Carbon atoms B.Pt ( o C)
© Boardworks Ltd 2003 Here are the boiling ranges of some fractions obtained from distillation of petroleum. 1. Using the previous graph, estimate the size range of the molecules present in each fraction. FractionBoiling Range ( o C) Number of carbons Fuel gasBelow 40 Petrol40 - 175 Kerosine150 - 240 Diesel220 - 275 1-5 5-10 9-14 13-17
© Boardworks Ltd 2003 The flammability of molecules 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.
© Boardworks Ltd 2003 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. SubstanceFlash Point Kerosine<23 Petrol85 - 150 Fuel Oil23 - 61
© Boardworks Ltd 2003 The viscosity of molecules 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.
© Boardworks Ltd 2003 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” The viscosity of molecules
© Boardworks Ltd 2003 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. HydrocarbonViscosity (cP) Pentane - C 5 H 12 0.40 Hexane - C 6 H 12 0.52 Heptane - C 7 H 16 0.24 Octane - C 8 H 18 0.92 Decane - C 10 H 22 0.70
© Boardworks Ltd 2003 The colour of molecules 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
© Boardworks Ltd 2003 The 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.
© Boardworks Ltd 2003 Using viscosity data for crude oil from different areas of the world, arrange the oils putting those with the smallest molecules first. CrudeOrderViscosity (cSt) Saudi Arabia47.7 UK (Brent)6.13 Norway (Gulifaks)16.5 Alaskan31.5 Malaysian3.43 1 2 3 4 5
© Boardworks Ltd 2003 Fuel gas Petrol / gasoline Naphtha Paraffin / Kerosine Diesel fuel Fuel and lubricating oil Bitumen Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas Fuel for cars and motorcycles, also used to make chemicals. Used to make chemicals. Fuel for greenhouse heaters and jet engines, manufacture of chemicals. Fuel for lorries, trains. Fuel for the heating systems of large buildings, fuel for ships, lubricating oil. Roofing, and road surfaces. Uses of each fraction
© Boardworks Ltd 2003 Burning hydrocarbons The apparatus below is used to test the products of combustion of a hydrocarbon. any hydrocarbon + oxygen water + carbon dioxide Suction pump Candle wax is the hydrocarbon here ice- water Liquid collected can be tested with anhydrous cobalt chloride paper (blue pink). Lime water
© Boardworks Ltd 2003 Which is a correct statement about crude oil? A.A mixture of carbohydrates. B.Formed by the decay of dead sea creatures. C.Consist of a mixture of very large molecules. D.Is purified in an oil rig.
© Boardworks Ltd 2003 Which is a correct statement about fractional distillation? A.Oil is separated into fractions with the same size molecule. B.Oil is separated into fractions with the same density. C.Oil is separated into fractions with similar size molecules. D.Oil is separated into alkanes and alkenes.
© Boardworks Ltd 2003 Which is a correct order for these fractions working down from the top of the column? A. Fuel gas, kerosine, petrol, diesel, bitumen. B. Fuel gas, diesel, kerosine, petrol, bitumen. C. Fuel gas, petrol, diesel, kerosine, bitumen. D. Fuel gas, petrol, kerosine, diesel, bitumen.
© Boardworks Ltd 2003 Which of these is a true statement about the changes that occur as hydrocarbon molecules get larger? A.Boiling point decreases. B.Viscosity increases. C.Flammability increases. D.Transparency increases.
The Haber Process The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is.
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