2 What do I need to know?Must Recall that crude oil is a mixture of a large number of compounds Should Define the term hydrocarbon Could Explain how the compounds in crude oil can be separated using physical methods including fractional distillation
3 Crude oilCrude oil is a mixture of a very large number of compounds and is made from the the bodies of plants and animals that have decayed many millions of years ago. A mixture is two or more substances NOT chemically combined together (such as a mixture of sand and water that can be separated by filtration).
4 HydrocarbonsMost of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only.We call these HYDROCARBONSWe can separate the different unchanged hydrocarbons from crude oil by FRACTIONAL DISTILLATION.
5 Fractional distillation Fractional distillation 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.Fractional distillation works because the different substances in the mixture have different boiling points.
7 Key points for exam questions To explain fractional distillation [3 marks]Heat crude oil to make it a gas/vapourCool to condenseHydrocarbons condense at different temperatures (boiling points).
8 Different hydrocarbon – different BP Different hydrocarbons have different numbers of carbon atoms.The higher the number of carbon atoms the higher its boiling point.
9 Key points for exam questions A fraction is a set of hydrocarbon molecules of similar size and similar boiling pointsDifferent fractions have different uses.Lighter fractions are more useful as fuels than heavier fractions.The petrol fraction and diesel fraction are key fractions for the oil industry.
14 ObjectivesMustRecall that most of the compounds in crude oil consist of hydrocarbons called alkanes.ShouldDescribe the general formula of an alkane and draw the structure.CouldExplain the naming of alkanes up to a chain length of four carbon atoms.
15 Carbon chainsAlkanes are chains of carbon atoms with hydrogen atoms attached to them.There is an alkane with one carbon atom, two carbon atoms, three, four, five and so on. The chains can be massive with hundreds of carbon atoms.You need be able to name and draw the first four and recognise some larger ones.
16 Methane One carbon atom bonded to four hydrogen atoms. Each line represents a single covalent bond.
17 Two carbon atoms six hydrogen atoms EthaneTwo carbon atoms six hydrogen atoms
19 Four carbon atoms ten hydrogen atoms ButaneFour carbon atoms ten hydrogen atoms
20 CnH2n+2 Can you spot a pattern? Every time we increase the number of carbons what happens to the number of hydrogens?We can work out a general formula for any alkane it is:CnH2n+2where n is the number of carbon atomsand 2n+2 is the number of hydrogen atoms
21 Counting in chemistryRather than the numbers 1,2,3 and 4 when we are counting in chemistry we use the terms:meth_ = 1eth_ = 2prop_ = 3but_ = 4The first four alkanes are therefore called methane, ethane, propane and butane.
25 Properties of hydrocarbons C1.4 Crude OilProperties of hydrocarbons
26 What do I need to know?Must recall the term alkane and the names for the first four alkanes in the series. State that these substances are commonly used as fuels. Should describe the difference between a saturated and an unsaturated hydrocarbon Could explain the boiling points, flammability and viscosity of hydrocarbon fuels.
27 Saturated and unsaturated EthaneEtheneAll single bondsFull of hydrogenSaturatedHas double bondFewer hydrogensUnsaturated
29 Liquid/GasFor this list of substance state whether liquid or gas at room temperature? The temperature when something boils is also the temperature when it condenses eg water boils at 100°C it also condenses at 100°CHydrocarbonBoiling point in °CSolid/Liquid/Gasmethane, CH4-162butane, C4H10pentane, C5H12+36decane, C10H22+175
30 Viscosity This simply means thickness of solution. For example water has a lower viscosity than treacleGenerally the higher the molecular weight (longer carbon chain) the more viscous the substance is.Bitumen has very long chain molecules and is very viscous and stick (tar).
33 ObjectivesRecall that most fuels contain carbon and/or hydrogen and may contain sulfur.Describe how, when a fuel burns gases are released into the atmosphere.Explain how the combustion of a fuel releases energy.
34 Hydrocarbon fuels We burn hydrocarbon fuels to release energy. Methane PropaneButanePetrolDieselKeroseneFuel oil+ many more
35 CombustionComplete combustion occurs when there is enough oxygen – for example when the hole is open on a Bunsen burner.The products of complete combustion are carbon dioxide and water.CH4 + 2O2 CO2 + 2H2O
37 Incomplete combustion Incomplete combustion occurs when there is not enough oxygen – for example when the hole is closed on a Bunsen burner.The products of incomplete combustion include carbon monoxide and carbon (soot). It is often called a sooty flame.
39 Carbon dioxide Carbon dioxide is a greenhouse gas. This means it causes global warming by trapping heat from the sun within the Earth’s atmosphere.
40 Carbon monoxideCarbon monoxide is an odourless and tasteless poisonous gas.If produced in an enclosed space it can be deadly.
41 Soot/smoke particlesParticles of carbon from incomplete combustion can be released into the atmosphere.This contributes to GLOBAL DIMMING
42 Other pollutantsSulphur present in fuels burns to produce sulphur dioxide.At high temperatures oxides of nitrogen may also be formed from nitrogen in the atmosphere.These react with water in the atmosphere to form ACID RAIN
43 Cleaning upUndesirable combustion products can be cleaned from emissions before they leave the chimney by using a filter or catalytic converter (cars).
49 What do I need to know?Recall that biofuels are produced from plant materialDescribe the fuels that can be produced from plant materialEvaluate the advantages and disadvantages of making fuel from renewable sources.
50 The problem with crudeCrude oil is a limited resource that will eventually run out.Alternatives are needed and some are already under development.
51 Ethical and environmental issues Clearance of rainforests to plant fuel cropsUsing land formerly used for food crop (causing hardship)Not replacing crops with sufficient crops after harvest for the process to remain carbon neutralErosion – replacing trees with crops with shallow roots
52 Carbon neutral – bioethanol, biodiesel and biomass Plants photosynthesise using carbon (dioxide) from the airBiodiesel/biothanol releases carbon (dioxide) from plantsPlants are replanted and photosynthesise, removing the carbon (dioxide) again.By contrast(fossil) diesel from crude oil releases ‘locked up’ carbon (dioxide) and doesn’t absorb any CO2