2 Hydrocarbons are molecules that contain carbon and hydrogen only. Crude oilCrude 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.
3 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.
4 Making oil usefulAlthough 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.
5 Fractional Distillation coolhotCrude 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.
6 Fractional Distillation coolhotCopy the column and arrange the fractions in the right order next to the arrows.Fuel gasPetroleumFractionBoiling Range(oC)KerosineDiesel220 – 275PetrolBitumen>350Fuel gasBelow 40Lubricating oilKerosineDieselLub. OilBitumen
8 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(oC)
9 Fraction Boiling Range (oC) Number of carbons 1-5 5-10 9-14 13-17 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.FractionBoiling Range(oC)Number of carbonsFuel gasBelow 40PetrolKerosineDiesel1-55-109-1413-17
10 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.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.Small moleculesBig moleculesMedium molecules
11 Uses of each fraction Fuel gas Petrol / gasoline Naphtha Paraffin / Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gasFuel gasPetrol/ gasolineFuel for cars and motorcycles, also used to make chemicals.NaphthaUsed to make chemicals.Paraffin /KerosineFuel for greenhouse heaters and jet engines, manufacture of chemicals.Diesel fuelFuel for lorries, trains.Fuel andlubricatingoilFuel for the heating systems of large buildings, fuel for ships, lubricating oil.BitumenRoofing, and road surfaces.
12 Which is a correct statement about crude oil? A mixture of carbohydrates.Formed by the decay of dead sea creatures.Consist of a mixture of very large molecules.Is purified in an oil rig.
13 Which is a correct statement about fractional distillation?Oil is separated into fractions with the same size molecule.Oil is separated into fractions with the same density.Oil is separated into fractions with similar size molecules.Oil is separated into alkanes and alkenes.
14 Which is a correct order for these fractions working down from the top of the column? Fuel gas, kerosine, petrol, diesel, bitumen.Fuel gas, diesel, kerosine, petrol, bitumen.Fuel gas, petrol, diesel, kerosine, bitumen.Fuel gas, petrol, kerosine, diesel, bitumen.
15 Which of these is a true statement about the changes that occur as hydrocarbon molecules get larger? Boiling point decreases.Viscosity increases.Flammability increases.Transparency increases.