Module C1.4

Crude oil and fractional distillation

Objectives

MustRecall that crude oil is a mixture of a large number of compoundsShouldDefine the term hydrocarbonCouldExplain 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?

Jet fuel

Petrol and diesel

Plastics and polymers

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.

Fractional distillation

Key points for exam questions

To explain fractional distillation [3 marks]1. Heat crude oil to make it a gas/vapour2. Cool to condense3. 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 fraction is 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 sampleshttp://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.

MethaneOne 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 atomsand 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

Mustrecall 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 hydrocarbonCould explain the boiling points, flammability and viscosity of hydrocarbon fuels.

Starter - Quiz

1. What is the name of the alkane with the formula CH4

2. What is the name of this alkane?

3. Draw a molecule of propane showing all the bonds.

Starter - Quiz

1. What is the name of the alkane with the formula CH4 - methane

2. What is the name of this alkane? ethane

3. Draw a molecule of propane showing all the bonds.

Spot the difference

Spot the difference

Ethane• All single bonds• Full of hydrogen• Saturated

Ethene• Has double bond• Fewer hydrogens• Unsaturated

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 or gaseous fuels

Liquid/Gas

For this list of substance state whether liquid or gas at room temperature?

Hydrocarbon Boiling point in °C Solid/Liquid/Gas

methane, CH4 -162

butane, C4H10 0

pentane, C5H12 +36

decane, C10H22 +175

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 combustionRemoving 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

AfL - Complete combustion

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.

AfL – incomplete combustion

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

Acid rain

Cleaning up

• Undesirable combustion products can be cleaned from emissions before they leave the chimney by using a filter or catalytic converter (cars).

Exam question 1d

Exam question 7c

Exam question 10

Exam question 10

Homework

• Now complete questions 11, 12 and 13 for homework.

C1.4 Crude Oil

Lesson 5 - Biofuels

Objectives

• Recall that biofuels are produced from plant material

• Describe the fuels that can be produced from plant material

• Evaluate the advantages and disadvantages of making fuel from renewable sources.

Starter

• Can you recall some of the uses of crude oil?

The problem with crude

• Crude oil is a limited resource that will eventually run out.

• Alternatives are needed and some are already under development.

Alternative fuels

• http://www.bp.com/liveassets/bp_internet/bpes_new/bpes_new_uk/STAGING/protected_assets/flash/secondary_resources/clip_bank/index.html#combustion_of_fuels

Ethical and environmental issues

• The video described some potential issues with biofuels.

• Can you describe any?

Ethical and environmental issues

• Clearance of rainforests to plant fuel crops• Using land formerly used for food crop

(causing hardship)• Not replacing crops with sufficient crops after

harvest for the process to remain carbon neutral

• Erosion – replacing trees with crops with shallow roots

Carbon neutral• Plants photosynthesise using carbon (dioxide) from

the air• Biodiesel/biothanol releases carbon (dioxide) from

plants • Plants are replanted and photosynthesise,

removing the carbon (dioxide) again.

• (fossil) diesel from crude oil releases ‘locked up’ carbon (dioxide) and doesn’t absorb any CO2

Different types of biofuels

• Ethanol – produced by fermentation of sugars in sugarcane

• Biodiesel – produced from hydrolysis of vegetable oils

Examination question Q14 (b)

Examination question Q14(b)

Mark scheme

Past paper question.

Mark scheme