Module C1.4 Crude oil and fractional distillation
Objectives 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
Starter • In your class books leave a gap to stick in your C1.3 booklets. • Write a new titles C1.4 Crude Oil
Starter • Video about crude oil (BP education) • Watch the video about crude oil and jot down answers to the following: • What is crude oil made of? • What do we use crude oil for?
Crude oil Crude 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).
Hydrocarbons • Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only. • We call these HYDROCARBONS • We can separate the different unchanged hydrocarbons from crude oil by FRACTIONAL DISTILLATION.
Uses of crude oil • Crude oil can be separated using a technique called FRACTIONAL DISTILLATION • Fractional distillation produces products we can use for lots of different applications. • What applications did you come up with?
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. • Click above link for BP Education service videos.
Key points for exam questions To explain fractional distillation [3 marks] • Heat crude oil to make it a gas/vapour • Cool to condense • Hydrocarbons condense at different temperatures (boiling points).
Different hydrocarbon – different BP • Different hydrocarbons have different numbers of carbon atoms. • The higher the number of carbon atoms the higher its boiling point.
Key points for exam questions • A fractionis a set of hydrocarbon molecules of similar size and similar boiling points
Plenary • Now attempt booklet questions • Q2(a) and 2(b). • Q3 (i) and (iii) • Q5 (a)(i) AND • Q6 (a)(i)
C1.4 Crude oil Lesson 2 - alkanes
Objectives Must • Recall that most of the compounds in crude oil consist of hydrocarbons called alkanes. Should • Describe the general formula of an alkane and draw the structure. Could • Explain the naming of alkanes up to a chain length of four carbon atoms.
Starter Oil samples Using BP oil samples http://www.bp.com/genericResource.do?categoryId=8043&contentId=7037455 Identify low molecular weight (gases), medium molecular weight (liquids) that can be obtained from fractional distillation of crude oil
Alkanes • Alkanes are the name of a type of chemical that makes up the compounds in crude oil. • They are hydrocarbons (contain only hydrogen and carbon) and form a series of increasing molecular weight.
Hydrocarbons video • http://www.bp.com/liveassets/bp_internet/bpes_new/bpes_new_uk/STAGING/protected_assets/flash/secondary_resources/clip_bank/index.html#properties_of_hydrocarbons
Carbon chains • Alkanes 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.
Methane One carbon atom bonded to four hydrogen atoms. Each line represents a single covalent bond.
Ethane Two carbon atoms six hydrogen atoms
Propane Three carbon atoms eight hydrogen atoms
Butane Four carbon atoms ten hydrogen atoms
AfL • Now attempt question 2(c) in your booklets. • Then attempt question 6(b) in your booklets • Then attempt question 9 in your booklets
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+2 where n is the number of carbon atoms and 2n+2 is the number of hydrogen atoms
Counting in chemistry • Rather than the numbers 1,2,3 and 4 when we are counting in chemistry we use the terms: • meth_ = 1 • eth_ = 2 • prop_ = 3 • but_ = 4 • The first four alkanes are therefore called methane, ethane, propane and butane.
C1.4 Crude Oil Lesson 3 – properties of hydrocarbons
Objectives 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.
Starter - Quiz • What is the name of the alkane with the formula CH4 • What is the name of this alkane? • Draw a molecule of propane showing all the bonds.
Starter - Quiz • What is the name of the alkane with the formula CH4 - methane • What is the name of this alkane? ethane • Draw a molecule of propane showing all the bonds.
Spot the difference Ethane Ethene Has double bond Fewer hydrogens Unsaturated • All single bonds • Full of hydrogen • Saturated
Properties • Some properties of hydrocarbons depend on the size of their molecules. • These properties influence how hydrocarbons are used as fuels. • Identify solids, liquids and gases in the following images…
Liquid/Gas For this list of substance state whether liquid or gas at room temperature?
Viscosity – new keyword • This simply means thickness of solution. • For example water has a lower viscosity than treacle • Generally 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).
Plenary - AfL • Attempt question 1(a) • Attempt question 8(a)
Burning Fuels Objectives: Complete combustion Incomplete combustion Removing impurites
Fuel Examples (where do they come from?) • Methane • Propane • Butane • Petrol • Diesel • Kerosene • Fuel oil • + many more
Combustion • Complete 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
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.
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.
Carbon monoxide • Carbon monoxide is an odourless and tasteless poisonous gas. • If produced in an enclosed space it can be deadly.
Soot/smoke particles • Particles of carbon from incomplete combustion can be released into the atmosphere. • This contributes to GLOBAL DIMMING
Other pollutants • Sulphur 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