Crude oil is separated into fractions using fractional distillation. Fractional distillation works by using a fractionating column to separate different hydrocarbon molecules based on their varying boiling points, which are determined by the intermolecular forces between the molecules. Larger hydrocarbon molecules have stronger intermolecular forces and higher boiling points, so they remain lower in the fractionating column, while smaller molecules have weaker intermolecular forces and lower boiling points, so they travel higher in the column. Cracking breaks down larger hydrocarbon molecules into smaller, more useful molecules to meet demand for fuels since crude oil contains too many large molecules.

1. Making Crude Oil Useful
Learning Intention
We are learning about how
Crude oil is separated into
fractions and why.
How and why fractional
distillation works.
To use data to evaluate the
use of different fuels
Keywords
& Phrases
Starter Activity
Look at the following formula displayed
on your starter activity sheet.
Write down two facts about each
molecule from its formula (3 marks)
Fractions
Distillation
Fuels
Crude Oil
Evaluate

2. Starter Activity
Look at the following formula displayed
on your starter activity sheet.
Write down two facts about each
molecule from its formula (3 marks)
Temperature
Saturated
Unsaturated
Family name
What Group?
General Formula
Bromine water
More reactive
Density
Intermolecular-force

3. Why is crude oil separated into
Fractions?
Watch video clip:
http://www.youtube.com/watch?v=26AN1LfbUPc

4. Fractional Distillation
i.
ii.
What is fractional
distillation?
Explain why crude oil
is separated by
fractional
distillation.
Use ideas about
 Size of molecules
 Forces between
molecules and how
these affect boiling
point.
May 2012 GCSE Q1 b)
http://www.ocr.org.uk/Images/135630-mark-scheme-unit-b641-02-unit-01-modules-c1-c2-c3-higher-tier-june.pdf

5. Fractional Distillation
Crude Oil
Mixture
Fractions
Boiling points
Large molecules
Small molecules
i. What is fractional distillation?
ii. Explain how and why fractional
distillation works.

6. More on properties of fractions
1. What can you say about the fractions that are
at the top of the column (in terms of its
boiling point – low or high?)
2. What can you say about bigger molecules
and its forces?

7. Properties of fractions
1. What can you say about the fractions that are
at the top of the column (in terms of its
boiling point – low or high?)
2. What can you say about bigger molecules
and its forces?
 Name the force between
them
 Intermolecular forces
 Strong attractive forces or
weak attractive forces?
 Easily separated or not?
 High boiling point  Low boiling point-

8. The Fractions In Crude Oil
Petrol contains the alkane with 8
carbons.
i. Can you guess its name?
ii. Draw a picture of the molecule.

9. Cracking
Cracking is used to make ethene.
Cracking needs a high temperature
and a catalyst. Write about
cracking.
Your answers should include
 What happens to hydrocarbon
molecules during cracking.
 Why cracking is a useful
reaction
May 2010 GCSE H-Tier Q 3(d)
http://www.ocr.org.uk/Images/61307-mark-scheme-unit-b641-02-unit-01-modules-c1-c2-c3-higher-tier-june.pdf

10. Cracking Large Molecules
The large molecules from crude oil can be
broken down (or cracked) into smaller, more
useful molecules.

11. Comparing Fuels – Peer Assessment
Task
You are going to peer assess
your work titled: Comparing
Fuels, based on the following
success criteria/benchmark.

12. Why Is Cracking Important?

13. Why Is Cracking Important?
Fuels made from oil mixtures
containing large hydrocarbon
molecules are not efficient. They do
not flow easily and are difficult to
ignite. Crude oil often contains too
many large hydrocarbon molecules and
not enough small hydrocarbon
molecules to meet demand - this is
where cracking comes in.

14. Plenary
60 seconds challenge – Sum Up

15. Self Assessment
You have 7 minutes
Self assessment – record
what you’ve learnt, any
difficulties you have had and
set your personal targets.

16. Cracking of Hexane
Hexane
C₆H₁₄  Butane + Ethene

17. Comparing Fuel Assessment Task
My Improvement target
5 minutes Task
Now your work has been
assessed, choose one or two
improvement targets using green
pen and the template provided.

18. Best Plenary tips
See tips shown in the link
http://www.teach-ict.com/teacher/plenary/plenaries.htm

19. Is used to separate c…………… o………. into
u………………..substances called f……………. in a fractionating
column. Each fraction is a mixture of h……………………… with
similar b………….. p………………
Fraction
Uses

20. Starter Activity
Look at the following formula displayed
on your starter activity sheet.
Write down two facts about each
molecule from its formula (3 marks)

23. Making Crude Oil Useful
Learning Intention
We are learning about how crude oil can be
separated into fractions.
How and why fractional distillation works.
How the forces between molecules affect their
boiling points.
i.
ii.
Know how fractional
distillation works
because of
differences
temperature.
To label fractional
distillation
apparatus.
Explain
Understand and apply the
concept of intermolecular
forces.
Explain why cracking
matches the supply and
demand of petrol.

24. Success Criteria
 Know how
fractional
distillation works
because of
differences
temperature.
 To label fractional
distillation
apparatus.
Explained that cracking
converts large alkanes
into smaller ones.
Showed detailed knowledge and
understanding of extraction methods and how
this relates to the reactivity series
Used equations where appropriate to explain
to the concept of cracking.
 Understand and apply
the concept of
intermolecular forces.
 Used equations where
appropriate to explain
to the concept of
cracking.
 Evaluate the use of
different fuels

25. Making Crude Oil Useful
Learning Intention
We are learning about how
Crude oil are separated into fractions and why.
How and why fractional distillation works.
To interpret and evaluate data to choose the best
fuel for a particular purpose.