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Transcript
The Production of Materials
1.
Fossil fuels provide both energy and raw materials such as ethylene, for the
production of other substances
CONSTRUCT WORD AND BALANCED FORMULAE EQUATIONS OF CHEMICAL REACTIONS AS THEY ARE ENCOUNTERED
Complete as encountered
GATHER AND PRESENT INFORMATION FROM FIRST-HAND OR SECONDARY SOURCES TO WRITE EQUATIONS TO
REPRESENT ALL CHEMICAL REACTIONS ENCOUNTERED IN THE HSC COURSE
Complete as encountered
IDENTIFY THE INDUSTRIAL SOURCE OF ETHYLENE FROM THE CRACKING OF SOME OF THE FRACTIONS FROM THE
REFINING OF PETROLEUM
•
•
•
•
Petroleum industries need to balance the production of hydrocarbon fractions to suit demand
Ethylene is a high demand hydrocarbon used to make polymers; however the fractional distillation of petroleum
does not produce enough to meet our needs
Because very little ethylene is found in natural gas or crude oil, it must be produced from other hydrocarbons by
a process known as ‘cracking’
Fractions used are higher molecular mass fractions for which there is less market demand. Products of cracking
include short chain alkanes that can be used as petrol, and alkenes, particularly ethylene.
Cracking: a chemical process by which hydrocarbons with higher molecular mass are converted to hydrocarbons of
lower molecular mass.
Thermal/Steam Cracking:
• Steam and alkanes are passed through metal coils. The steam removes carbon deposits from the metal coils and
the heat breaks bonds forming ethylene from alkanes.
Catalytic Cracking
•
•
•
𝑧𝑒𝑜𝑙𝑖𝑡𝑒 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡
C 10 H 22(g) �⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯� C 8 H 18(g) + C 2 H 4(g)
Zeolite catalysts are aluminosilicates consisting of aluminium, silicon and oxygen
o Effective because of their large surface area per unit of mass.
o The zeolite catalysts adsorb the reactants, weakening their bonds and reducing activation energy for the
reaction
Can be carried out at lower temperature (500⁰C) than steam cracking, and with greater control of products
formed
Pg 1-2
IDENTIFY THAT ETHYLENE, BECAUSE OF THE HIGH REACTIVITY OF ITS DOUBLE BOND, IS READILY TRANSFORMED INTO
MANY USEFUL PRODUCTS
As an alkene, ethylene is unsaturated and has a double C=C bond, unlike the single C-C bonds of alkanes. The main
reactions that alkanes can undergo are combustion, and UV-induced halogenation. In alkenes, the double bond can be
changed into a single bond, giving each carbon atom an extra bonding capacity with which ethylene can form new bonds
with other molecules/atoms, in an addition reaction
• These products include a range of very useful products such as ethanol, pharmaceuticals, explosives,
insecticides and the starting materials of several important plastics / polymers.
• Addiction reactions are characteristic of alkenes.
• Addiction reaction: two new atoms or molecules are ‘added’ across the double bond, one to each carbon atom
linked by the double bond. This converts the C=C double bond to a C-C single bond.
• Addition polymer: A long chain formed from the bonding
together of smaller molecules (monomers) in which no
other product is formed. Unlike condensation polymers in
which small molecules are released, all atoms present in the
monomer are also present in the polymer.
• Hydrogenation: addition of hydrogen
 CH 2 =CH 2(g) + H 2(g)  CH 3 -CH 3(g)

Ethylene + hydrogen  ethane
Heating ethylene with hydrogen in
presence of metal catalyst e.g. nickel
Halogenation: addition of halogens
o These reactions are useful for distinguishing
between saturated hydrocarbons e.g. alkanes, and
unsaturated hydrocarbons e.g. alkenes
o Unsaturated hydrocarbons decolourise yellowbrown bromine water
o Alkanes will not react unless exposed to ultraviolet
light (substitution reactions)
 CH 2 =CH 2(g) + Br 2(aq) + H 2 O (l)  CH 2 OH
•
CH 2 Br + HBr (aq)

Ethylene + bromine dissolved in water  2bromoethanol + hydrogen bromide

*1,2-dibromoethane may also be produced
Reaction of ethylene with chlorine produces 1,2-dichloroethane, which is used to manufacture
chloroethylene, and then PVC
o 1,2-dibromoethane used as a petrol additive
Hydrohalogenation: addition of hydrogen halides
o
•
•
•

CH 2 =CH 2(g) + HCl (g)  CH 3 -CH 2 Cl (l)

Ethylene + hydrogen chloride  chloroethane
Hydration: addition of water
o Ethanol is prepared industrially from ethylene by addition of water in presence of sulfuric acid catalyst
 CH 2 =CH 2(g) + H 2 O (l)  CH 3 -CH 2 OH (l)
 Ethylene + water  ethanol
o Ethanol can be used as a disinfectant, anti-freeze, industrial solvent and even an alternate fuel source
for vehicles
Oxidation
Product
Formula
Use
𝐴𝑔 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡
o C 2 H 4 + ½ O 2 �⎯⎯⎯⎯⎯⎯⎯� CH 2 OCH 2
Polyethylene
(CH 2 ) n
Plastic
 Ethylene + oxygen  ethylene oxide
o

•
𝐻+
CH 2 OCH 2 + H 2 O �� CH 2 OH-CH 2 OH
Ethylene oxide + water  1,2-ethanediol
Ethylene oxide
(CH 2 ) 2 O
Steriliser
1,2,-ethanediol
CH 2 OHCH 2 OH
Manufacture of
polyester and
PET plastics,
automotive
antifreeze
Ethanol
C 2 H 5 OH
Disinfectant,
anti-freeze,
solvent and fuel
for vehicles
Ethanoic acid
CH 3 COOH
Food
preservative
o 1,2-ethanediol can be used as antifreeze in cars
Polymerisation (to make polyethylene)
Pg 3-4
IDENTIFY THAT ETHYLENE SERVES AS A MONOMER FROM
WHICH POLYMERS ARE MADE
•
•
•
Ethylene is also used to make intermediate compounds
which can then undergo polymerisation reactions
E.g. poly(styrene), PVC
Main use of ethylene is to make the polymer poly(ethylene)
•
•
•
Polymer: large molecule consisting of small repeating units called monomers joined together by covalent bonds
Polymerisation: chemical reaction by which monomers become linked to form polymers
IDENTIFY POLYETHYLENE AS AN ADDITION POLYMER AND EXPLAIN THE MEANING OF THIS TERM
•
•
Addition polymerisation: monomers add to growing polymer chain in such a way that all the atoms present in the
monomer are also present in the polymer (i.e. there is no other product)
o Involve unsaturated monomers with C=C double bond joining together.
o Polyethylene is an addition polymer
Condensation polymerisation involves a reaction between two different functional groups in which a molecule of
water (or some other small molecule) is eliminated and the two functional groups become linked together.
OUTLINE THE STEPS IN THE PRODUCTION OF POLYETHYLENE AS AN EXAMPLE OF A COMMERCIALLY AND
INDUSTRIALLY IMPORTANT POLYMER
Pg 5-7:
•
LDPE: Low density polyethylene
o 1000-3000 atmospheres pressure, and 300⁰C temperature, along with an initiator (organic peroxide)
o Process forms low-density polyethylene which has significant branching; leading to relatively disorganised,
open structure, which lowers strength of polyethylene
 Initiation: Organic peroxide free radical adds on to ethylene molecule, making an initiator-ethylene
free radical
 Propagation: Chain lengthens as reactive molecule reacts with other ethylene molecules, forming a
long chain of molecules.
 Termination: Combination of two free radical chains pairs up 2 unpaired electrons, terminating
chain propagation.
•
HDPE: High density polyethylene
o Zeigler-Natta process uses 2-3 atmospheres pressure, 60⁰C temperature, and a catalyst
o Catalyst is mixture of titanium (III) chloride and a trialkylaluminium compound
o Produces a more crystalline polyethylene, which has higher density and is stronger
IDENTIFY THE FOLLOWING AS COMMERCIALLY SIGNIFICANT MONOMERS:
VINYL CHLORIDE
STYRENE
BY BOTH THEIR SYSTEMATIC AND COMMON NAMES
Pg 8-11:
• Vinyl chloride produced from ethylene, chlorine and oxygen, using CuCl 2 catalyst and 150⁰C temperature
• Poly(vinyl chloride) formed from vinyl chloride, using either ‘heat’ or ‘free radical’
• Styrene produced from ethylene and benzene using aluminium chloride catalyst and heat
Monomer
Polymer
Common name
Systematic name
Common name
Systematic name
Ethylene
Ethene
Poly(ethylene)
Poly(ethene)
Vinyl chloride
Chloroethene
PVC
Poly(chloroethene)
Chloroethylene
Poly(vinyl chloride)
Styrene
Ethenyl benzene
Poly(styrene)
Poly(ethenyl benzene)
Vinyl benzene
Phenyl ethene
o Always use (…) around polymer names, systematic AND common
DESCRIBE THE USES OF THE POLYMERS MADE FROM THE ABOVE MONOMERS IN TERMS OF THEIR PROPERTIES
Factors affecting properties of polymers:
• Average chain length: longer polymers have larger molecule mass, and hence greater dispersion forces, making
them stronger
• Arrangement of chains with respect to each other: crystalline regions where molecules are closely packed
result in a stronger polymer. Amorphous regions produce weaker and more flexible plastics
• Degree of branching: more branching restricts orderly arrangement, and hence reduces hardness and increases
flexibility
• Cross-linking between polymer chains: covalent cross-linking in thermosetting plastics make polymer very hard
and difficult to melt. When heated, these plastics decompose instead of melting.
• Functional groups in monomer units: Polar functional groups increase intermolecular forces between
molecules. –OH and –NH 2 groups result in hydrogen bonding, and increase hardness of the plastic. Large sidegroups can stiffen the chain and decrease flexibility
•
Inclusion of additives: Additives include plasticisers to soften the material, or flame retardants.
Name
Properties
Used for
LDPE
•
low density, soft, flexible, transparent/translucent,
electrical insulator, thermoplastic, impermeable to water
•
•
•
flexible shopping bags
food wrap
squeeze botles
HDPE
•
high density, hard to semi-flexible, opaque, high tensile
strength, thermoplastic, impermeable to water,
chemically resistant
•
•
•
crinkly garbage bags
rubbish bins
milk crates
made flame resistant and flexible with additives,
impermeable to water, thermoplastic
•
•
•
rigid pipes and gutters
hose pipes
electrical insulation in
house wiring
extension cords
flexible raincoats
shower curtains
Poly(vinylchlor •
ide)
•
•
•
Poly(styrene)
•
rigid, unreactive, transparent due to few crystals, when
gas added forms foam, low density, heat/cold insulator,
resists high impact, thermoplastic
•
•
•
•
tool handles
compact disc cases
foam drinking cups
heat insulation
Pg 9-11: …
IDENTIFY DATA, PLAN AND PERFORM A FIRST-HAND INVESTIGATION TO COMPARE THE REACTIVITIES OF
APPROPRIATE ALKENES WITH THE CORRESPONDING ALKANES IN BROMINE WATER
ANALYSE INFORMATION FROM SECONDARY SOURCES SUCH AS COMPUTER SIMULATIONS, MOLECULAR MODEL KITS
OR MULTIMEDIA RESOURCES TO MODEL THE POLYMERISATION PROCESS
2.
Some scientists research the extraction of materials from biomass to reduce
our dependence on fossil fuels
DISCUSS THE NEED FOR ALTERNATIVE SOURCES OF THE COMPOUNDS PRESENTLY OBTAINED FROM THE
PETROCHEMICAL INDUSTRY
•
Biomass: organic matter derived from living organisms
•
•
•
•
•
Petrochemicals are chemicals made from compounds in petroleum or natural gas. Fossil fuels are non-renewable
resources.
Currently, Australia has petroleum reserves that will last about 35 years, and natural gas reserves that will last 125
years. Fossil fuels take millions of years to accumulate, and over 95% of these are burned as a source of energy.
As petroleum supplies diminish the cost will increase.
If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are
used up.
There is also a need to find alternative sources of fuel, because using petroleum-based fuels causes global warming
via the enhanced greenhouse effect
Pg 19
EXPLAIN WHAT IS MEANT BY A CONDENSATION POLYMER
And
DESCRIBE THE REACTION INVOLVED WHEN A CONDENSATION POLYMER IS FORMED
Pg 12-13:
• Condensation polymerisation involves a reaction between two functional groups in which a molecule of water (or
some other small molecule) is eliminated and the 2 functional groups become linked together.
• For example, when two glucose monomer molecules react through two hydroxyl groups -OH, a H-OH molecule
(water) is condensed out, leaving an -O- linking the two monomer molecules. The first two glucose molecules to join
condense out an H-OH, and every glucose molecule added to the growing chain then condenses out another H-OH.
• Monomers of 6-aminohexanoic acid join by peptide links [-CO-NH-], releasing molecules of water. This forms nylon6
DESCRIBE THE STRUCTURE OF CELLULOSE AND IDENTIFY IT AS AN EXAMPLE OF A CONDENSATION POLYMER FOUND
AS A MAJOR COMPONENT OF BIOMASS
•
•
•
•
Cellulose is main constituent of plant cell walls, and major structural component of woody plants and natural fibres
e.g. cotton
Most abundant polymer in the biosphere
• Large proportion of world’s biomass is in the form of cellulose
Made up of thousands of glucose monomers
Β-linkages in cellulose (bulky CH 2 OH groups on alternating sides) result in formation of flat, ribbon-like strands
o
•
Close packing of these ribbons and strong hydrogen bonds between them gives cellulose its strength
and rigid structure.
The reduced availability of hydroxyl groups in the cellulose structure, due to their involvement in hydrogen bonding
between the chains, makes it insoluble in water and resistant to chemical attack.
Pg 20-21
IDENTIFY THAT CELLULOSE CONTAINS THE BASIC CARBON-CHAIN STRUCTURES NEEDED TO BUILD PETROCHEMICALS
AND DISCUSS ITS POTENTIAL AS A RAW MATERIAL
•
A 3 carbon-chain and a 4 carbon-chain are present within the structure of a glucose monomer in a cellulose chain,
and have attached hydrogen/hydroxyl groups
• Many polymers are made using 3 carbon monomers (such as polypropylene in Australian 'paper' currency) or 4
carbon monomers (such as those used to make synthetic rubbers).
• The carbon-chain sections in cellulose could be changed to chemicals that at present mostly made from petroleum,
if a chemical processes can be developed or micro-organisms found that can break the cellulose into glucose
monomers, and glucose into three carbon-chains and four carbon-chains.
• Thus biomass, a renewable resource, could be used to make polymers instead of fossil fuels, a non-renewable one.
1) Cellulose (Broken down by steam/acid pre-treatment, then hydrolysis using the enzyme cellulase)
o The reduced availability of hydroxyl groups in the cellulose structure, due to their involvement in
hydrogen bonding between the chains, makes it insoluble in water and resistant to chemical attack.
2) Glucose (Broken down by yeast/distillation)
3) Ethanol (Broken down by catalysed dehydration)
4) Ethylene (Source for petrochemical industry)
______________________________________________________________________________
• Plastics made from cellulose would be biodegradable, biocompatible and renewable
• Existing biopolymer chains in plant material can be modified
o Cellulose nitrate is a synthetically modified cellulose that was widely used for photographic and movie
film early this century. It was also used as an explosive and a plastic called celluloid. Unfortunately it
was highly flammable and was replaced.
o Cellulose acetate, which is much less flammable, is used today for overhead projector slides.
o Rayon is another polymer derived from modified cellulose
USE AVAILABLE EVIDENCE TO GATHER AND PRESENT DATA FROM SECONDARY SOURCES AND ANALYSE PROGRESS IN
THE RECENT DEVELOPMENT AND USE OF A NAMED BIOPOLYMER. THIS ANALYSIS SHOULD NAME THE SPECIFIC
ENZYME(S) USED OR ORGANISM USED TO SYNTHESISE THE MATERIAL AND AN EVALUATION OF THE USE OR
POTENTIAL USE OF THE POLYMER PRODUCED RELATED TO ITS PROPERTIES
•
Biopolymer: a naturally occurring polymer produced by living organisms, including plants, animals and
microorganisms
o Biopolymers are biodegradable, biocompatible and renewable
Pg 14-19:
Poly(3-hydroxybutyrate)
• Bacteria ‘Alcaligenes eutrophus’ are grown in fermentation vats with high conc. glucose, lowered conc.
nitrogen, and 30⁰ temperature
• PHB produced up to 80% of bacteria’s dry weight.
•
•
•
PH3B is extracted using solvents like halogenated hydrocarbons which break bacterial cell walls and separate
plastic from cell debris.
PHB is then milled to a powder/pellets
Properties and uses
o Thermoplastic: can be melted, moulded, shaped into various forms
o Similar to polypropylene, but biodegradable, biocompatible and renewable
o Degrades slowly in the body, and is biocompatible/non-toxic
 Potentially used as controlled drug-release carrier
 Used in stitches/sutures
o Biodegradability is a disadvantage for many applications where the plastic must not break down over
time
o Breaks down in anaerobic conditions of landfill
 Disposable nappies, bottles, bags, packaging materials
o Good oxygen permeability
 Use as wrapping film
o Similar physical properties to polypropylene: brittle, rigid, crystalline, high tensile strength, high MP
 Brittle nature limits its use
o Copolymers, e.g. with 3-hydroxy pentanoate (to make BioPol), are more flexible, and hence have more
applications and potential use in the future
o High production costs (5-7 x petrochemical plastics) limits its use currently
3.
Other resources, such as ethanol, are readily available from renewable
resources such as plants
DESCRIBE THE DEHYDRATION OF ETHANOL TO ETHYLENE AND IDENTIFY THE NEED FOR A CATALYST IN THIS PROCESS
AND THE CATALYST USED
•
•
•
•
•
•
Before ethylene could be produced from catalytic cracking of petroleum, ethylene was produced primarily from
dehydration of ethanol
o Dehydration: chemical reaction where water is removed from a compound
o Heating ethanol vapour over a catalyst at 350⁰C.
o Effectively, the –OH group is removed, a hydrogen atom is removed from an adjacent carbon atom,
which form a water molecule
o This leaves the adjacent carbon atoms with an unfilled outer shell, changing their C-C single bond to a
C=C double bond.
In the past, aluminium oxide catalyst was used; today porous ceramic crystals are used
Catalyst is needed because the ethanol molecule is stable, and will not spontaneously break bonds to release
a water molecule and form a double bond.
As a dehydrating agent, sulfuric acid removes water , promoting the forward reaction (Le Chatelier’s Principle)
In the lab, catalyst used is an excess of concentrated sulfuric acid, or phosphoric acid
o A zeolite catalyst can also be used, which provides very reactive site
350⁰C temperature, (ethanol is in gaseous state)
o C 2 H 5 OH (g)  C 2 H 4(g) + H 2 o (g)
DESCRIBE THE ADDITION OF WATER TO ETHYLENE RESULTING IN THE PRODUCTION OF ETHANOL AND IDENTIFY THE
NEED FOR A CATALYST IN THIS PROCESS AND THE CATALYST USED
•
Ethanol can be made in 2 ways: fermentation of sugars, hydration of ethylene
o Hydration: chemical reaction where water is added to a compound
•
•
•
•
•
o Most industrial ethanol is made by hydration since ethylene is a low-cost material
Reverse of dehydration of ethanol
o Reaction is carried out with an excess of high-pressure steam
Catalyst is needed because water molecule itself will not attack the electrons in the ethylene double bond
o The electron-rich double bond is likely to be attacked by an ion that has an electron deficiency (e.g. H+
ion); and so acid catalysts are used
o Also, the reaction occurs very slowly without a catalyst; a catalyst is needed to make the reaction
proceed at a fast rate by lowering activation energy
Catalyst used is dilute sulfuric acid
300⁰C temperature (water in the form of steam)
In industry, highly acidic zeolite catalysts are used instead, due to problems with safety and environment when
using sulfuric acid
o C 2 H 4(g) + H 2 O (g)  C 2 H 5 OH (g)
PROCESS INFORMATION FROM SECONDARY SOURCES SUCH AS MOLECULAR MODEL KITS, DIGITAL TECHNOLOGIES OR
COMPUTER SIMULATIONS TO MODEL:
- THE ADDITION OF WATER TO ETHYLENE
- THE DEHYDRATION OF ETHANOL
DESCRIBE AND ACCOUNT FOR THE MANY USES OF ETHANOL AS A SOLVENT FOR POLAR AND NON-POLAR
SUBSTANCES
•
•
•
•
•
•
•
Ethanol is a common solvent in cosmetics (perfume), solvent-based paints, dyes, food colourings, household
cleaning products, pharmaceuticals, and in industry
Sold domestically as methylated spirits
o 95% ethanol, 5% poisonous methanol, and some foul-tasting chemicals to discourage people from
drinking it. Called denatured ethanol
The –OH end is polar (hydrophilic), because the C-O and O-H bonds are polar, due to oxygen’s high
electronegativity
o Ethanol dissolves polar substances such as chloroform, CHCl 3 , and common ether with dipole-dipole
forces
o Can form hydrogen bonds with many other substances, and so can dissolve these [mostly organic]
substances readily
 E.g. glucose, sucrose, carboxylic acids, amino acids, and some proteins
 Because of hydrogen bonding, ethanol is miscible with water in any proportion. [completely
miscible]
Because the alkyl part (CH3-CH2-) is non-polar (hydrophobic), ethanol can also dissolve non-polar substances,
as it forms dispersion forces between hydrocarbon end and non-polar substance
o Allows ethanol to dissolve non-polar iodine, and short-chain hydrocarbons like pentane/heptane
o Miscible in hexane as well as water
If hydrocarbon chain was lengthened (e.g. pentanol), it could not dissolve in water; if hydrocarbon chain was
shortened (e.g. methanol), it would not be miscible in other hydrocarbons
*Ethanol is used as a solvent in dissolving substances that do not dissolve easily in water. Once the non-polar
material is dissolved in the ethanol, water is added to prepare a solution that is mostly water.
o E.g. perfumes: *Since ethanol has a lower boiling point, it quickly evaporates off the skin due to body
heat, leaving the necessary fragrant chemicals on the skin.
*Used in household cleaning products, because the non-polar alkyl end forms dispersion forces with non-polar
grease, then polar –OH end allows the cleaning solution/grease to be washed away by water
o *Ethanol is least toxic of the alkanols
Ethanol can form hydrogen bonds with water:
OUTLINE THE USE OF ETHANOL AS A FUEL AND EXPLAIN WHY IT CAN BE CALLED A RENEWABLE RESOURCE
•
•
•
•
Ethanol can undergo combustion, and may be used as a fuel
o Combustion generates 1367 kJ of heat per mole of ethanol
Blending ethanol with petrol (e.g. E10) produces fuels that produce less pollution, contribute less to the
greenhouse effect, and reduce the use of non-renewable petroleum supplies
o Presence of oxygen in ethanol itself leads to cleaner combustion and less soot/carbon monoxide
Ethanol can also be used as a portable fuel for camping stoves, in the form of methylated spirits
Ethanol is a renewable resource
o Can be made from glucose, unlike petrol which is made from limited petroleum supplies
 Glucose is obtained from plant material with a high starch/simple-sugar content
• E.g. wheat, maize, potatoes, grapes, molasses, sugar cane
• Since plant matter is a renewable resource, ethanol is a renewable resource
o When burnt, it forms carbon dioxide and water; these were used in the production of ethanol (they are the
reactants for photosynthesis in plants), and so can be converted back into ethanol
o Ethanol, after being broken down into carbon dioxide and water via combustion, can ultimately reformed
back into ethanol, and hence can be called a renewable resource
DESCRIBE CONDITIONS UNDER WHICH FERMENTATION OF SUGARS IS PROMOTED
•
•
•
•
•
•
Suitable source of sugar mashed up with water (in this case sugar cane)
Yeast added
Very low concentrations of oxygen to prevent aerobic respiration
o A small concentration of oxygen must be provided to the fermenting yeast as it is a necessary
component in the biosynthesis of polyunsaturated fats and lipids
Small amount of yeast nutrients such as phosphate salts
Mixture kept at 37⁰C
o Note*: fermentation is an exothermic process
Mixture kept in the dark
SUMMARISE THE CHEMISTRY OF THE FERMENTATION PROCESS
and
PRESENT INFORMATION FROM SECONDARY SOURCES BY WRITING A BALANCED EQUATION FOR THE FERMENTATION
OF GLUCOSE TO ETHANOL
•
Cane sugar waste is rich in sucrose. If water and yeast are added, the sucrose reacts with water producing
glucose and fructose, which can be fermented by the yeast.
o C 12 H 22 O 11 + H 2 O  C 6 H 12 O 6 + C 6 H 12 O 6
o Sucrose + water  glucose + fructose
•
Fermentation
𝑦𝑒𝑎𝑠𝑡
o C 6 H 12 O 6(aq) �⎯⎯� 2 C 2 H 5 OH (aq) + 2 CO 2(g)
o Glucose/fructose  ethanol + carbon dioxide
SOLVE PROBLEMS, PLAN AND PERFORM A FIRST-HAND INVESTIGATION TO CARRY OUT THE FERMENTATION OF
GLUCOSE AND MONITOR MASS CHANGES
DEFINE THE MOLAR HEAT OF COMBUSTION OF A COMPOUND AND CALCULATE THE VALUE FOR ETHANOL FROM
FIRST-HAND DATA
Molar heat of combustion: the heat liberated when one mole of a substance undergoes complete combustion to
produce CO 2 and H 2 O under standard conditions of temperature and pressure.
IDENTIFY DATA SOURCES, CHOOSE RESOURCES AND PERFORM A FIRST-HAND INVESTIGATION TO DETERMINE AND
COMPARE HEATS OF COMBUSTION OF AT LEAST THREE LIQUID ALKANOLS PER GRAM AND PER MOLE
ASSESS THE POTENTIAL OF ETHANOL AS AN ALTERNATIVE FUEL AND DISCUSS THE ADVANTAGES AND
DISADVANTAGES OF ITS USE
ADVANTAGES:
•
•
•
Ethanol is a renewable resource, and would reduce usage of non-renewable fossil fuels (if less fossil fuel was
used to make ethanol than would normally be used as a fuel)
o Made from glucose (crops), unlike petrol which is made from limited petroleum supplies
 Local oil reserves expected to run out in a few decades, so using renewable ethanol fuel, can
make petroleum supplies last longer
• Saving petroleum for petrochemicals
o When burned, it forms carbon dioxide and water; these were used in the production of ethanol, and can
be converted back into ethanol
Using ethanol would reduce greenhouse gas emissions (if less CO 2 was released in production of ethanol than
would normally be released from the combustion of fossil fuels)
o Carbon dioxide liberated by combustion of ethanol, was absorbed from atmosphere by crops from
which ethanol is produced
 i.e. ethanol is ‘CO 2 neutral’, whereas burning fossil fuels releases carbon dioxide which was
trapped underground
Cars using ethanol fuel produce fewer pollutants, especially carbon monoxide, than cars running on petrol
o One mole of octane requires more oxygen to burn than one mole of ethanol. Hence, petrol is more likely
to undergo incomplete combustion than ethanol.
o Also, oxygen in ethanol provides oxygen for combustion reaction, allowing complete combustion to
occur.
 Reduces carbon monoxide and soot emissions, and hence pollution
o Toxic ‘anti-knock’ additives such as MTBE that provide oxygen don’t need to be added to the fuel
DISADVANTAGES:
•
•
•
•
•
Ethanol may not be a renewable resource
o More fossil fuels may need to be burned for the energy used in the production of ethanol, than is saved
by using ethanol as a fuel instead of fossil fuels
Ethanol may not reduce greenhouse gas emissions
o More energy is needed to grow the crops, fertilise them, transport them, and for the distillation process 7
 This energy would most likely come from the combustion of fossil fuels
 If this is compared to carbon dioxide released by combustion of octane, more carbon dioxide is
produced per unit of energy produced by ethanol, than by octane
o Hence, ethanol as a fuel may contribute more to the greenhouse effect than petrol.
 Currently, there have been no reliable studies to show whether ethanol made in Australia
produces less greenhouse gas overall than the petrol it replaces
Large areas of agricultural land would be needed to grow suitable crops
o Environmental problems such as soil erosion, deforestation, fertiliser runoff and salinity
o Habitat loss
o Reduces area available for subsistence food crops
Disposal of smelly waste fermentation liquors after the removal of ethanol presents environmental problems
Petrol with more than 10-20% ethanol has detrimental effect on vehicles
o Engines and fuel lines must be modified to use 100% ethanol, because ethanol is corrosive, and has
different burn characteristics
 Cost of setting up factories to make a totally new engine design, makes 100% ethanol unlikely in
the near future
Ethanol has a high potential as an alternative fuel, mainly because it is a renewable resource. It is made from
sugars present in sugar cane, maize, molasses, etc. As such, it can reduce the use of dwindling petroleum
supplies. Also, combustion of ethanol is neutral with respect to the greenhouse effect. Cars running on
ethanol also release less carbon monoxide and soot, as the oxygen from ethanol promotes complete
combustion without toxic additives such as MTBE.
However, with current technology, the fossil fuels used and carbon dioxide released in the production of
ethanol from crops may outweigh the amount of fossil fuel usage that ethanol replaces. Therefore, ethanol as
an alternative fuel is currently not much better than oil from a greenhouse effect viewpoint. Other
disadvantages include the large areas of arable land which would be needed to grow suitable crops, and the
disposal of the smelly waste fermentation liquors after the removal of ethanol, both of which present
environmental problems.
Economic feasibility has also limited the use of ethanol as an alternative fuel in the past. However, in light of
increasing awareness of climate change, the greenhouse effect, and our dwindling petroleum supplies,
ethanol has a good potential as an alternative fuel, especially if efficient production of glucose from cellulose
can be done, and renewable energy sources used to provide energy for the production processes, e.g. solar
energy for distillation. Genetic engineering of yeast to increase ethanol concentration to greater than 15% is
also an area of active research.
PROCESS INFORMATION FROM SECONDARY SOURCES TO SUMMARISE THE PROCESSES INVOLVED IN THE INDUSTRIAL
PRODUCTION OF ETHANOL FROM SUGAR CANE
•
•
•
Sugarcane is mashed/shredded, and mixed with water
Cane juice mixed with lime to adjust pH to about 7
Cane juice is concentrated until sugar crystallises out
•
•
•
•
•
Centrifuge is used to separate sugar from molasses (the remaining liquid)
*Blackstrap molasses collected as by-product of the manufacture of cane sugar
o Ethanol produced from a normally useless waste product
Molasses diluted to a less concentrated mash
pH adjusted to about 4-5 using mineral acid
Yeast is added, and fermentation occurs for 1-3 days
o Conditions for fermentation
 Suitable source of sugar mashed up with water (in this case sugar cane)
 Yeast added
 Very low concentrations of oxygen to prevent aerobic respiration
• A small concentration of oxygen must be provided to the fermenting yeast as it is a
necessary component in the biosynthesis of polyunsaturated fats and lipids (0.05 – 0.10
mm Hg oxygen tension) 9
 Mixture kept at 37⁰C
 Small amount of yeast nutrients such as phosphate salt 1
o Yeasts are susceptible to ethanol inhibition; growth rate halts at 10%, cells die at 14% due to ethanol
toxicity
o Zymase is the ‘enzyme complex’ which catalyses the reaction
o Yeast used is Saccharomyces Cereviciae
o 90-95% of theoretical yield is produced, as some of the substance is used up by the yeast
o Fermentation is an exothermic process
o C 6 H 12 O 6(aq)  2CH 3 CH 2 OH (aq) + 2CO 2(g)
•
•
Fermented product (6-10% ethanol) is sent to the purification section
Fractional distillation of the ethanol/water produces a higher concentration of ethanol (96%)
o Distillation takes about half of the energy released when ethanol is burned
 In the future, low energy methods may be used such as passing the solution through zeolite
filters which act as molecular sieves
• Polar water molecules attracted to polar parts of zeolite, while less polar ethanol passes
through
o Alternative dehydration processes may be used to concentrate ethanol higher than 96% such as:
 Azeotropic distillation by adding benzene
•
For alternative sources of biomass other than sugar cane, acids and cellulase enzymes are some of the ways that
are being looked into to hydrolyse the more complex carbohydrates (e.g. cellulose) in the crop into simpler
sugars such as sucrose and glucose.
PROCESS INFORMATION FROM SECONDARY SOURCES TO SUMMARISE THE USE OF ETHANOL AS AN ALTERNATIVE
CAR FUEL, EVALUATING THE SUCCESS OF CURRENT USAGE
•
•
In 1970’s, Brazil attempted to grow sugar cane to supply ethanol as a fuel
o Purpose: to reduce consumption of non-renewable fuels, and to use locally produced and plentiful
sugar cane instead of expensive imported oil
o Brazilian government subsidised production of ethanol by sugar cane fermentation.
o At peak in 1980s, Brazil produced 16 billion litres of fuel ethanol per year.
o Disrupted food production farming to make way for ‘ethanol farming’ and was an economic failure
 1990: Ethanol shortage and lowered oil prices resulted in consumers switching back to petrolethanol mixtures.
o As oil prices increase again, consumers are shifting again towards using ‘flex-fuel’ vehicles that can run
on any proportion of ethanol and petrol
Petrol with 10-20% ethanol can be used in ordinary engines without any modification
o
o
o
Car manufacturers oppose higher than 10% ethanol in petrol on the grounds that it has a detrimental
effect on vehicles.
 Fuel with 10% ethanol, 90% petrol, is called E10.
Federal government planning to restrict petrol to contain no more than 10% ethanol
Engines must be modified to use 100% ethanol, because ethanol is corrosive, and has different burn
characteristics
 *Cost of setting up factories to make a totally new engine design, makes 100% ethanol unlikely
in the near future
•
Devoting large areas of land to growing crop (monocropping) for the production of ethanol may not be
economically feasible in a modern context
o Currently in Australia, sugar cane wastes are the source of sugars for fermentation to ethanol
 Use of sugar industry wastes (molasses) is not enough to totally replace petrol with ethanol
o Some argue that using agricultural land and crops for fuel production, has caused food prices to
skyrocket in recent times
 A UN report says that biofuels have caused world food prices to go up by 75%
•
Ethanol costs more than petrol to produce, even though it can be made from waste products like molasses
o Australian government has set up subsidies to encourage production of ethanol to be added to petrol
o Distillation takes about half of the energy released when ethanol is burned
o Most of the agricultural products used to produce ethanol, command higher prices as food
o Agricultural products often have a low ethanol yield, and high transport costs
Use of 100% ethanol fuel seems unlikely, unless:
o Efficient production of glucose from cellulose (crop wastes) can be done
o Renewable energy sources used to provide energy for distillation process
Cars using ethanol fuel produce fewer pollutants, especially carbon monoxide, than cars running on petrol
o One mole of octane requires more oxygen to burn than one mole of ethanol. Hence, petrol is more likely
to undergo incomplete combustion than ethanol.
o Also, oxygen in ethanol provides oxygen for combustion reaction, allowing complete combustion to
occur
 Reduces carbon monoxide and soot emissions, and hence pollution
o Toxic additives such as MTBE that provide oxygen don’t need to be added to the fuel
•
•
IDENTIFY THE IUPAC NOMENCLATURE FOR STRAIGHT-CHAINED ALKANOLS FROM C1 TO C8
Methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol
4.
Oxidation-reduction reactions are increasingly important as a source of
energy
EXPLAIN THE DISPLACEMENT OF METALS FROM SOLUTION IN TERMS OF TRANSFER OF ELECTRONS
•
•
•
Displacement reactions: oxidation-reduction reactions in which one of the products is displaced from solution as a
separate phase
Metal displacement reactions: Oxidation-reduction reactions in which one metal reduces the ions of another metal
into a neutral atom displacing it from solution as a separate phase, and itself becomes an ion
E.g. iron nail dissolves when placed in a solution of copper sulphate
o Fe (s) + Cu2+ (aq)  Fe2+ (aq) + Cu (s)
o Transfer of electrons from iron metal to copper(II) ions, occurs on the surface of iron nail
o This occurs because Cu2+ ions have a
greater tendency to gain electrons than
Fe2+ ions, and so Cu2+ ions will accept
electrons from Fe metal.
Pg 23:
• More active metal displaces less active metal from
solution, because a more active metal atom loses one or more electrons to become a cation. These electrons
are transferred to the less active metal, reducing it into elemental form
IDENTIFY THE RELATIONSHIP BETWEEN DISPLACEMENT OF METAL IONS IN SOLUTION BY OTHER METALS TO THE
RELATIVE ACTIVITY OF METALS
•
•
Metals can be arranged into an activity series by their ability to displace one another from solution
An activity series is a list of metals arranged in order of decreasing ease of oxidation
o Any metal can be oxidised by the ions of a less reactive metal
Pg 23:
• The more reactive a metal, the more readily it gives up electrons. Metals which have a greater tendency to give
up electrons are more reactive than those that have a lesser tendency to give up electrons
• A more active metal will displace the metal ion of a less active metal from solution, because it gives up electrons
more easily than the ion.
ACCOUNT FOR CHANGES IN THE OXIDATION STATE OF SPECIES IN TERMS OF THEIR LOSS OR GAIN OF ELECTRONS
•
•
Oxidation states help us keep track of the number of electrons transferred in oxidation-reduction reactions
o The oxidation state of an element in a compound is the number of electrons transferred to or from
the neutral atom when the compound is formed
An increase in oxidation state represents oxidation, so an atom must lose electrons to increase its oxidation
state
o Oxidation states are therefore a useful way of determining whether an oxidation-reduction reaction has
taken place.
Oxidation States:
- of elements in their elemental form is 0 including diatomic elements O 2
- of neutral compounds is 0
- sum of oxidation states of atoms in a neutral compound equals 0
- oxidation state of ion, or the sum of oxidation states of atoms in the radical, equals the charge
- of oxygen is -2 except peroxide is -1
- of hydrogen is +1 except hydride is -1
Pg 24:
• Oxidation: a loss of electrons, increase in oxidation number, loss of hydrogen or gain of oxygen
• Reduction: a gain of electrons, decrease in oxidation number, gain of hydrogen or loss of oxygen
DESCRIBE AND EXPLAIN GALVANIC CELLS IN TERMS OF OXIDATION/REDUCTION REACTIONS
and
OUTLINE THE CONSTRUCTION OF GALVANIC CELLS AND TRACE THE DIRECTION OF ELECTRON FLOW
•
•
•
•
•
Description of galvanic cell
o Consists of 2 half-cells. Each half-cell consists of an electrode (conductive metal/graphite strip in contact
with an electrolyte solution). Electrolyte solutions are joined by salt bridge containing an electrolytic
solution e.g. KNO 3 . Salt bridge may consist of filter paper saturated with KNO 3 solution. External circuit
connects the electrodes in the two half-cells
In terms of oxidation/reduction reactions
o A galvanic cell physically separates oxidation and reduction reactions, so that the movement of
electrons occurs through an external circuit (constituting a current). A salt bridge connects the two halfcells to carry charged ions in solution. A galvanic cell is thus composed of two half-cells, a reductant
half-cell where oxidation occurs (anode) and an oxidant half-cell where reduction occurs (cathode).
Oxidation always occurs at the anode
o For a galvanic cell, the anode is negative (electrons produced)
Reduction always occurs at the cathode
o For a galvanic cell, the cathode is positive (electrons accepted)
Daniel cell: reaction between metallic zinc and copper(II) sulphate
o Zinc ions go into solutions and hence zinc strip slowly dissolves
o Zn (s)  Zn2+ (aq) + 2e-
o
Electrons given up by zinc pass through external circuit to copper strip. At the cathode they’re accepted
by copper(II) ions in solution, reducing them to copper atoms which deposit on the strip. Removal of
Cu2+ ions from solution causes a colour change from blue to colourless
o Cu2+ (aq) + 2e-  Cu (s)
o
For each zinc ion produced, a copper(II) ion is removed from solution. Electrical neutrality in solutions is
maintained by migration of positive
ions towards copper half-cell and
negative ions towards zinc half-cell
 Zn2+ ions move into salt
bridge, NO 3 - ions move
into zinc half-cell
 SO 4 2- ions move into salt
bridge, K+ ions move into
copper half-cell
Cell diagram: Zn | Zn2+ || Cu2+ | Cu
• The single vertical line represents the
boundary between phases. The double
vertical line represents a salt bridge
through which ions can move
• Pt, H 2(g) | H+ || Au3+ | Au
o Anode is hydrogen gas bubbling
over platinum electrode, in H+
solution. Cathode is gold electrode
dipping into Au3+ solution
• Pt, H 2(g) | H+, Cl- | Cl 2(g) , Pt
o Cathode is hydrogen gas bubbling over platinum electrode. Anode is chlorine gas bubbling over
platinum electrode. Both electrodes share a common HCl (aq) electrolyte. There is no double line ||
because there is no salt bridge.
• Pt | I 2 , I || Fe3+, Fe2+ | Pt
Cathode is platinum electrode dipping into solution of iodine and iodide ions. Anode is platinum
electrode dipping into solution of Fe3+ and Fe2+ ions. There is no single vertical line | between Fe3+ and
Fe2+ because they are in the same phase. Rather, the boundary between phases is between the
platinum electrode, and the solution of both iron ions.
The zinc electrode alone is denoted by Zn | Zn2+
o
•
Pg 26-28:
• Function of salt bridge:
o To complete the circuit
o Allows movement of ions to neutralise build-up of ions in each beaker.
• *If one reactant is going from elemental to ionic, and the other from ionic to elemental form, then two beakers
with two electrolyte solutions are needed, as the initially ionic reactant may directly react with the initially
elemental one.
o E.g. If Zn|| Cu galvanic cell had a common electrolyte, zinc metal would directly displace copper ions
• *If both reactants are going from elemental to ionic state, then one beaker with a common electrolyte solution
may be used, as the reactants cannot react with each other directly since they’re physically separated initially,
and neither the elemental anode or cathode can react directly with any ions in the common electrolyte
o E.g. H 2 ||Cl 2 galvanic cell
Pg 26-28:
• Direction of electron flow is from anode to cathode
DEFINE THE TERMS ANODE, CATHODE, ELECTRODE AND ELECTROLYTE TO DESCRIBE GALVANIC CELLS
Pg 26-28:
• Anode: Electrode at which oxidation occurs
• Cathode: Electrode at which reduction occurs
• Electrode: Electrical conductors in contact with electrolyte solution; the interface where oxidation/reduction
occurs (often made of metal, graphite, or inert platinum)
• Electrolyte: any substance containing mobile ions that behaves as an electrically conductive medium
o In the case of galvanic cells, these are the ionic solutions. The electrolyte must not react with any ions in
the 2 solutions it is connecting.
PERFORM A FIRST-HAND INVESTIGATION TO IDENTIFY THE CONDITIONS UNDER WHICH A GALVANIC CELL IS
PRODUCED
PERFORM A FIRST-HAND INVESTIGATION AND GATHER FIRST-HAND INFORMATION TO MEASURE THE DIFFERENCE IN
POTENTIAL OF DIFFERENT COMBINATIONS OF METALS IN AN ELECTROLYTE SOLUTION
GATHER AND PRESENT INFORMATION ON THE STRUCTURE AND CHEMISTRY OF A DRY CELL OR LEAD-ACID CELL AND
EVALUATE IT IN COMPARISON TO ONE OF THE FOLLOWING:
- BUTTON CELL
- FUEL CELL
- VANADIUM REDOX CELL
- LITHIUM CELL
- LIQUID JUNCTION PHOTOVOLTAIC DEVICE (EG THE GRATZEL CELL)
IN TERMS OF:
- CHEMISTRY
- COST AND PRACTICALITY
- IMPACT ON SOCIETY
- ENVIRONMENTAL IMPACT
•
Pg 30-35
Cost & Practicality
Dry Cell (Leclanché Cell)
Fuel Cell
•
•
Cheap to produce
Can be used for a variety of things
•
•
•
•
Fairly large for their small voltage
(1.5V)
Can leak
Slowly go flat as voltage drops off
gradually
Short shelf life because zinc anode
reacts with acidic NH 4 + ions
If current is drawn rapidly, NH 3 gas
builds up, causing a drop in voltage
Primary cells: cannot be recharged
Many portable devices can be used
Continuous supply of <1.23V
High fuel efficiency (80-90%)
Long operating lifetime (50,000 hours)
•
•
Expensive as it is a developing technology
Auxiliary systems that feed reactants into
cell and remove products are expensive
Liquid cooling systems needed
Pure hydrogen required, as impurities
poison Pt catalyst
Theoretical e.m.f. of 1.23 V hard to
achieve, as movement of H+ ions through
electrolyte is a limiting factor
Long operating lifetime (50,000 hours)
•
•
•
•
Impact on Society
•
•
•
•
•
•
•
•
Environmental Impact
•
•
•
without mains power supply
Changed our way of life: efficient,
cheap, easily transportable devices
e.g. radios
Resulted in a much more mobile
society
Chemicals within a dry cell are not as
damaging to environment as other
chemicals in other batteries
Zinc, a heavy metal, is toxic to
animals
Since these are primary cells, they
can take up a lot of space in landfills,
where build-up of chemicals like zinc
can occur
•
•
Developing technology for hydrogen fuel
that may replace petroleum fuel
Used in space shuttles
•
•
Non-polluting, as only water is produced
Hydrogen and oxygen reactants are
plentiful
•
Storage of explosive hydrogen required
SOLVE PROBLEMS AND ANALYSE INFORMATION TO CALCULATE THE POTENTIAL
REQUIREMENT OF NAMED
ELECTROCHEMICAL PROCESSES USING TABLES OF STANDARD POTENTIALS AND HALF-EQUATIONS
Pg 29:
• Only potential difference between two cells coupled together can be measured. It is necessary to use a
reference half-cell, so that individual half-cell potentials can be compared
• The hydrogen half-cell consists of hydrogen gas at a pressure of 1 atmosphere, bubbling around an inert
platinum electrode in a solution of 1M hydrogen ions:
• Hydrogen half-cell is given an
value of 0.00 V
• The standard reduction potential,
, of an electrode, is the potential of that electrode in its standard state
(1M for any solutes, 1 atm for any gases) relative to the standard hydrogen electrode, with standard conditions
of 101.3 kPa pressure and 25⁰C temperature
• A positive
value means that an electrode has a greater tendency to accept electrons and be reduced than
the hydrogen system. A negative
value means that an electrode has a greater tendency to lose electrons
and be oxidised than the hydrogen system.
•
values are not voltages, they are a measure of electromotive force (e.m.f.). The e.m.f. of a galvanic cell is
the potential difference across the electrodes when a negligibly small current is being drawn.
5.
Nuclear chemistry provides a range of materials
DISTINGUISH BETWEEN STABLE AND RADIOACTIVE ISOTOPES AND DESCRIBE THE CONDITIONS UNDER WHICH A
NUCLEUS IS UNSTABLE
Pg 37-38:
• A stable isotope’s nucleus doesn’t change
• A radioactive isotope has an unstable nucleus which releases particles/energy to become more stable.
o Any isotope with atomic number > 83, is unstable
o Stability of nucleus also depends on neutron-to-proton ratio.
o Most stable nuclei are found in an area of graph known as the ‘zone of stability’
• Radioactivity is the spontaneous change in composition of an unstable nucleus leading to the emission of
radiation.
•
Alpha-decay
o Occurs when there are too many protons AND
neutrons (nucleus too heavy)

•
Beta-decay
o Occurs when there are too many neutrons for
the # of protons present. A neutron turns into
a proton and electron
o Mass number remains same, atomic number
+1, electron emitted

•
Carbon-14: 14 6 C  14 7 N + 0 -1 e
Positron emission
o Occurs when there are too many protons for
the # of neutrons present. A proton becomes a
neutron and positron
o Mass number remains same, atomic number 1, positron emitted

•
U-238: 238 92 U  234 90 Th + 4 2 He
K-38: 38 19 K  38 18 Ar + 0 1 e
Electron capture
Occurs when there are too many protons for the #
of neutrons present. An inner-orbital electron is
captured by the nucleus, converting a proton into a neutron
 Hg-201: 201 80 Hg + 0 -1 e  201 79 Au
•
Gamma radiation
o Emission of high energy photons enables nucleus to lose excess energy and become more stable
DESCRIBE HOW TRANSURANIC ELEMENTS ARE PRODUCED
Pg 38:
• Transuranic elements are those that follow uranium in the periodic table. Uranium has the highest atomic
number of a natural element (92)
• Elements of atomic number >92, have to be made synthetically by bombarding nuclei with neutrons in a nuclear
reactor, or with charged nuclei e.g. α particles in a particle accelerator.
• Neptunium and plutonium were synthesised by bombarding uranium-238 with neutrons
o
•
•
238
92 U
+ 1 0 n  239 92 U 239 93 Np + 0 -1 e
239
93 Np
 239 94 Pu + 0 -1 e
Only three of the transuranic elements, those with atomic numbers 93, 94 and 95, have been produced in
nuclear reactors.
Transuranic elements from atomic number 96 and up are all made by accelerating a small nucleus (such as He, B
or C) in a charged particle accelerator to collide with a heavy nucleus (often of a previously made transuranic
element) target.
DESCRIBE HOW COMMERCIAL RADIOISOTOPES ARE PRODUCED
In induced nuclear transformations, the target nucleus is bombarded with various particles. These particles may
become incorporated within the target nucleus, creating a new unstable nuclide.
Pg 39-40:
•
•
Nuclear reactors produce neutron-rich radioisotopes
o Neutrons are uncharged and so don’t need to be accelerated, to be absorbed
o Source of neutrons is by fission reactions in fission reactor

o
Sample to be irradiated is placed in the core of the reactor, where it absorbs neutrons.
o
98
42 Mo
+ 1 0 n  99 42 Mo
99
42 Mo
 99m 43 Tc + 0 -1 e
99m
43 Tc
 99 43 Tc + γ
o ANSTO operates the HIFAR nuclear reactor at Lucas Heights
•
Particle accelerators produce neutron deficient radioisotopes
o An accelerator is needed to overcome electrostatic repulsion, so that target nucleus can be bombarded
with a charged particle
o Cyclotron: Used to produce radioisotopes for medical use
 Charged particles are accelerated in a spiral path
o

o
o
98
42 Mo
+ 2 1 H  99m 43 Tc + 1 0 n
ANSTO operates the National Medical Cyclotron at Sydney’s Royal Prince Alfred Hospital
Synchrotron: Used in research into the composition of materials
 Can accelerate protons to 90% of speed of light
Linear accelerators: Used for radiation therapy and physics research
 Produces high-energy electrons
IDENTIFY INSTRUMENTS AND PROCESSES THAT CAN BE USED TO DETECT RADIATION
Scintillation counter: Low energy radiation that is too weak to ionise atoms is called non-ionising radiation and can be
detected by a scintillation counter. The non-ionising radiation transfers energy to a fluorescent molecule that emits
light. A photomultiplier produces an amplified electrical pulse from the light. A counter counts the pulses.
Pg 44-45:…
PROCESS INFORMATION FROM SECONDARY SOURCES TO DESCRIBE RECENT DISCOVERIES OF ELEMENTS
•
The nineteen transuranic elements with the atomic numbers above 95 require high-energy particle accelerators
to be produced.
•
Heaviest element produced as of 2005 is element 116, with the IUPAC systematic name of ununhexium (symbol
Uuh). This was produced in 2000 by bombarding curium atoms with calcium nuclei
o
•
248
96 Cm
+ 48 20 Ca  292 116 Uuh + 41 0 n
Element 110 (Darmstadtium) (Ds) was made in collision between lead and nickel nuclei
o First discovered at GSI in 1994, but different observations produced different isotopes of the new
element
o In 1998, GSI team produced 271 110 Ds, by accelerating a beam of nickel-64 nuclei to an energy of 209 MeV
and directly it at a lead-208 target
o The team observed alpha-decay sequences which signalled production and decay of 271 110 Ds
o
208
82 Pb
+ 64 28 Ni  271 110 Ds + 1 0 n
IDENTIFY ONE USE OF A NAMED RADIOISOTOPE:
- IN INDUSTRY
- IN MEDICINE
Pg 41-43:
• In industry: Strontium-90 used in thickness gauges to control thickness of sheet materials
• In medicine: Technetium-99m used in medical tracer diagnosis
DESCRIBE THE WAY IN WHICH THE ABOVE NAMED INDUSTRIAL AND MEDICAL RADIOISOTOPES ARE USED AND
EXPLAIN THEIR USE IN TERMS OF THEIR CHEMICAL PROPERTIES
Pg 41-43:
Technetium-99m
• A gamma camera builds up an image based on the points from which radiation is emitted
• Chemical properties of technetium-99m enable it to be combined with other compounds to study different
areas of the body
o E.g. combined with tin compound, it attaches to red blood cells, whereupon blood flow can be traced.
o Combined with glucose, it accumulates in parts of the body where glucose is concentrated
Strontium-90
Radiation loses energy as it passes through matter, proportional to thickness/density of the material. Strontium-90 is a
beta/gamma emitter used in thickness gauges to control thickness of sheet materials.
•
90
38 Sr
 90 39 Y + 0 -1 e + γ
If the material is too thick, less radiation passes through to the detector, causing rollers to increase pressure on the
material to reduce thickness. If material is too thin, more radiation passes through to detector, causing rollers to
decrease pressure to increase material’s thickness.
Strontium-90 can be used in a chemically inert form sealed in a container, enabling equipment to have a long lifetime
without regular maintenance
Also, the heat generated by strontium-90's radioactive decay can be converted to electricity for long-lived, portable
power supplies called ‘radioisotope thermoelectric generators’. These are often used in remote locations, such as in
navigational beacons, weather stations, and space vehicles.
USE AVAILABLE EVIDENCE TO ANALYSE BENEFITS AND PROBLEMS ASSOCIATED WITH THE USE OF RADIOACTIVE
ISOTOPES IN IDENTIFIED INDUSTRIES AND MEDICINE
Benefits:
• Disinfecting and extending shelf-life of food without need for harmful chemicals to humans. This allows food to
be stored longer before being consumed and allows for less wastage of spoiled foods and without harmful
additives to humans in the food.
• Medical diagnosis and treatment by non-intrusive radioisotopes means patients do not have to have surgery.
Radiation therapy allows patients to be treated for cancer without the need for extensive operation which may
not be able to take out all the cancer and takes a long time to heal from
Strontium-90:
Strontium-90 is ideal because it:
• Has a long half-life of 28 years, and so won’t have to be replaced very often
• Low energy emission, and so minimises radiation dose as well as ensuring that sheet absorbs most of the radiation
Problems:
• Highly reactive chemically (reacts with air) and so must be isolated from air
Radiation can cause electrons to be removed from atoms and molecules, and can:
• Affect structure of enzymes so they no longer function
• Alter DNA structure, causing cancer
• Alter sex cells, causing defects in offspring
• People who work with radioisotopes in medicine, industry and research must take precautions, including carrying a
radiation badge, wearing face masks, or protective clothing.
================
• As strontium is chemically similar to calcium (same number of valence electrons), it may be incorporated into
bones, causing leukaemia and bone cancer
• Strontium-90 decays to Yttrium-90, which is a beta emitter which a much shorter half-life of 64 hours
o Yttrium-90 poses a risk of burns to eyes and skin due to fast decay