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?
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/vapour
2. Cool to condense
3. 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 samples
http://www.bp.com/genericResource.do?categoryId=8
043&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/b
pes_new/bpes_new_uk/STAGING/protected_
assets/flash/secondary_resources/clip_bank/i
ndex.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
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
methane, CH4
-162
butane, C4H10
0
pentane, C5H12
+36
decane, C10H22
+175
Solid/Liquid/Gas
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
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
by
trapping heat from the sun within the Earth’s
atmosphere.
Carbon monoxide
• Carbon monoxide is an odourless and
tasteless
.
• 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
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
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/b
pes_new/bpes_new_uk/STAGING/protected_
assets/flash/secondary_resources/clip_bank/i
ndex.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