Year 12 Chemistry
HSC topics

Production of Materials

The Acidic environment

Chemical monitoring and management

Option: Industrial Chemistry, Shipwrecks corrosion and Conservation,
Biochemistry of Movement, Chemistry of Art, Forensic Chemistry
http://discovery.kcpc.usyd.edu.au//9.2.1/9.2.1_CrackingCatalytic.html
Focus Area 1: Fossil fuels provide both energy and raw materials such as
ethylene, for the production of other substances
Fossil fuels are formed from the remains of organisms that lived on Earth millions of
years ago. Fossil fuels are rich in hydrocarbons that can be burnt to release energy or
used to make raw materials such as ethylene.
Chemicals derived from petroleum are collectively called
petrochemicals.
Ethylene is the same substance as ethene. Ethene is the
IUPAC name for C2H4 while ethylene is the name that is
more commonly used in industry.
Ethylene (C2H4) can be used to produce useful substances such as polyethylene and
ethanol.
Polyethylene is the cheapest plastic. The weight of polyethylene produced each year
is greater than the total weight of all other plastics. Most plastic food bags, juice and
milk containers are made of, or lined with, polyethylene.
Need to do: Revise: hydrocarbon naming
Identify the industrial source of ethylene from the cracking of some of the
fractions from the refining of petroleum
Fractional distillation of crude oil is used to separate it into its fractions. The
consumer demand for these different fractions does not match the proportions in
crude oil as shown below.
Fraction
% in crude oil % by consumer demand
Petrol
35
45
Diesel
25
27
Kerosene 20
<5
Bitumen
2
10
The demand for petrol exceeds supply produced by fractional distillation of crude oil.
Petroleum is a mixture of hydrocarbons. When petroleum undergoes fractional
distillation, some fractions, particularly petrol, are in demand and of high economic
value. Other fractions, consisting of larger molecules than in petrol and of low value,
can be passed over a heated catalyst that cracks the larger molecules into smaller
molecules. A major by-product of this catalytic cracking is ethylene, also known as
ethene.
Catalytic cracking is the process in which high molecular weight fractions from
crude oil are broken into lower molecular weight substances in order to increase
the output of high demand products.
Cracking can occur at lower temperatures (500OC) by using a zeolite (crystalline
aluminosilicate substance) catalyst. The gaseous fraction is absorbed by the zeolite,
weakening the bonds and reducing Ea (activation energy).
-eg-
C18H38 (g)
zeolite
4 CH2=CH2 (g) +
C10H22 (g)
Steam cracking converts ethane and propane into ethene. The ethane (from natural
gas deposits) and steam are passed (at around 900OC) through very hot metal tubes to
decompose the alkanes.
-eg-
C2H6 (g)
CH2=CH2 (g)
+
H2 (g)
C3H8 (g)
CH2=CH2 (g)
+
CH4 (g)
Copy Down Example of cracking (shown below)
Homework Questions- Week 1
1. Describe the composition of petroleum
2. When petroleum undergoes distillation, fractions are produced. Identify some
of these.
3. Define fractional distillation
4. Use a diagram to show the industrial process of fractional distillation of
petroleum.
5. Identify the IUPAC name for ethylene
6. Construct the structural formula for ethylene.
7. Outline the main source of ethylene.
8. Ethene is produced by the cracking of petroleum fractions. Describe the
process of cracking.
identify data, plan and perform a first-hand investigation to compare the reactivities of
appropriate alkenes with the corresponding alkanes in bromine water
Alkanes undergo substitution reactions
Alkenes undergo addition reactions as they have reactive double bonds
Bromine water is a yellow-brown colour, as it reacts with a hydrocarbon the yellow
brown colour disappears leaving a clear solution.
Aim: To compare the reactivity of an alkane and an alkene.
Materials:

4 Test tubes

Bromine water (BrOH)

Alkane (cyclohexane C6H12)

Alkene (cyclohexene C6H10)

Fume Cupboard
Justify the use of these materials
Hypothesis
Hints: Cyclohexane and cyclohexene are both colourless liquids. Is this important? You could also compare the toxicity of these
cyclic hydrocarbons and similar straight chain hydrocarbons. Why is bromine water used here? Will is show a different reaction
rate for an alkane and an alkene.
Hints: From the theoretical knowledge of alkanes and alkenes, predict which will be more reactive and write this as a statement
that can be tested.
Variables: identify the following variables in the experiment
Independent variable
Dependent variable
Controlled variables
Hint: this is the one thing you change in
Hint: This is what you measure or
Hint: these are the things that must
your experiment.
observe to see the reaction.
remain the same throughout the
experiment.
Risk Assessment: (MSDS- material safety data sheet) Before you carry out the
experiment you must carry out a risk assessment. This identifies any risk involved by
using the equipment you are using.
Chemicals and equipment
Risk
Describe the precaution
Explain the precaution
Bromine water
Toxic and corrosive
Use a fume cupboard,
Prevent toxic substances
goggles and gloves. Work in
being ingested, splashed into
a well ventilated area. Do not
the eyes or contacting the
discard in the skin but place
skin.
in an organic waste disposal.
Toxic substances would enter
the environment and could
enter the food chain and
cause poisoning.
Cyclohexane
Toxic, harmful if swallowed
Cyclohexene
Method: Follow the procedure and note any modifications you make.
1. Carry out this procedure in a fume cupboard and wear gloves and safety
goggles.
2. Pour 1 mL cyclohexane into each of 2 test tubes labeled A and B.
3. Pour 1 mL cyclohexene into each of 2 test tubes labeled C and D.
4. Cover test tubes A and C so they are in the dark.
5. Place test tubes B and D in the sunlight.
6. Add 5 drops bromine water to each test tube.
7. Tap the side of the test tube gently to mix the contents.
8. Observe any colour change.
Results:
Hint: Describe any colour changes observed in each test tube and how long it took for the colour to change. Remember that you
must always describe results as changing form one colour to another. Do not use the word ‘clear’ when you mean colourless.
Test Tube
Initial colour of
Initial colour of
Colour after
hydrocarbons
bromine water
bromine water
added to
alkene/alkane
A
B
Time for change
C
D
Write equations in words and symbols.
Discussion:
Account for your results: Hint: Were they what you expected?
Comment on the accuracy of your results.
Hint: Could the colour change be readily observed? Were the
same quantities of chemicals used in each test tube to allow for accurate results?
Comment on the reliability of your results Hint: Was the experiment carried out more than once to check if
the results were reliable.
Comment on the validity of your investigation Did the design of your experiment allow you to test what
you set out to test? Did you have a control?
Conclusion: Complete the following statements to write a conclusion for this experiment. You must make sure that your
conclusion answers your aim and hypothesis.
The results support/ do not support the hypothesis. The alkene, cyclohexene, reacted
quickly/slowly with bromine water, changing colour from __________ to _________.
This happened even in the light/dark.
The alkane, cyclohexene, reacted quickly/very slowly with bromine water in the
dark/light and did not react when in the light/dark.
Reactions of Alkanes and Alkenes.
There are only 2 important reactions:
1. Combustion: alkanes burn in air to form carbon dioxide and water and as part
of the process a large amount of heat is released.
Example: C3H8 (g)+ 5O2 (g)  3CO2 (g) + 4H2 O (g)
2. Alkanes such as ethane undergo substitution reactions. This is a reaction in
which an atom is substituted for another already in the molecule, e.g. A
hydrogen atom may be replaced with a halogen atom. Light energy is
required.
Example: CH4 (g) + Cl2 (g)  CH3Cl (g) + HCl (g)
identify that ethylene, because of the high reactivity of its double bond, is readily
transformed into many useful products
Ethylene is a more reactive molecule than ethane or other alkanes. The high reactivity
of its double covalent bond that allows it to be chemically transformed into a wide
variety of useful products. There are many substances which react with alkenes by
opening out the double bond to form two
single bonds: these are called addition
reactions.
Cyclohexene
1,2dibromocyclohexane
Products derived from ethylene:
Product
Use
Polyethylene
Plastic film, crates and pipes
Ethylene dichloride
Raw material used to make the vinyl
chloride monomer for PVC production
Polyvinylchloride (PVC)
Plastic pipes, guttering, soft furnishings
Ethanol
Solvent, fuel and drinks
Ethylene glycol
Antifreeze
Polystyrene
Plastic packaging, insulation
1,2-dibromoethane
Petrol additive
Chloroethane
Solvent, refrigerant
Reaction of ethene with water to produce ethanol- industrially this reaction is
performed at high pressure at 300C and using phosphoric acid as a catalyst.
Ethanol belongs to a group called alkanols, they can be regarded as alkanes with one
H atom being replaced by an OH group.
Ethanol is widely used as a reactant and a solvent in the synthesis of products ranging
from pharmaceuticals to nail varnishes and plastics.
Write a balanced equation for the reactions of (i) hydrogen (using a catalyst) (ii)
chlorine (iii) bromine water
a. propene
b. 2-butene
c-c=c-c
identify that ethylene serves as a monomer from which polymers are made
identify polyethylene as an addition polymer and explain the meaning of this term
What is a monomer?
(need to type out notes that are in folder)
Paperclip- monomer, paperclip chain- polymer
What is a polymer?
Examples:
outline the steps in the production of polyethylene as an example of a commercially
and industrially important polymer
Use textbook page 13-15 to complete table comparing LPDE and HDPE
identify the following as commercially significant monomers:
vinyl chloride - styrene
by both their systematic and common names
See notebook presentation, also used modeling kits.
describe the uses of the polymers made from the above monomers in terms of their
properties
Bring in examples of polymers, and in terms of their properties.
analyse information from secondary sources such as computer simulations, molecular
model kits or multimedia resources to model the polymerisation process

Use modelling kits.
http://www.lbl.gov/MicroWorlds/Kevlar/KevClue1Act1.html
Focus Area 2: Some scientists research the extraction of materials from biomass
to reduce our dependence on fossil fuels
Assignment:
Alternatives to petrochemicals
Condensation polymer- what is and reaction involved in
Cellulose as and example
Focus area 3: other resources such as ethanol are readily available from
renewable resources such as plants
Focus area 4: oxidation-reduction reactions are increasing important as a source
of energy
Focus area 5:nuclear chemistry provides a range of materials