9.2 Production of Materials – Yr 12 2008
Written by Sam Jiang
1. Fossil fuels provide both energy and raw materials such as ethylene, for the
production of other substances
 Identify the industrial source of ethylene from the cracking of some of the
fractions from the refining of petroleum.
Ethene (IUPAC or systematic name), Ethylene is a material that present in trace amounts in
nature and it is produced by cracking petroleum, those are various fractions produced by
fractional distillation of crude oil, called petrochemical feedstock.
Process used to produce ethylene and other small china hydrocarbons is called cracking. It
takes the raw material crude oil (very long chains of hydrocarbon) and splits it up into
smaller parts. Whenever an alkane is cracked, an alkene always results as one of the by
products.
There are three types of cracking:
 Steam cracking 750-900 degrees Celsius
(A) Initiation
Hydrocarbon chins split at high temperature into fragments, they become free radicals and
are reactive as they have unpaired electrons.
(Decane to Pentyl free radicals)
(B) Propagation
Free radicals decompose to produce smaller free radicals and release alkenes.
(Pentyl free radical to propyl radical + ethylene)
(C) Termination
Free radicals may react with other free radicals to form hydrocarbon molecules.
(propyl radical+ propyl radical to hexane)
 Thermal cracking
 Catalytic cracking 500 degrees Celsius and 200kPa pressure
Used to boost yield of petrol to meet demand
During catalytic cracking, octane and zeolite (inorganic compound, often aluminosilicate)
are commonly used. Endothermic process, air is excluded to prevent explosion with oxygen.
Catalytic cracking lowers activation energy to allow the process to be achieved at a lower
temperature and reduces fuel consumption. Surface area is important in cracking, the
molecules bond with the surface of the catalyst breaks the carbon-carbon bond.
 Identify that ethylene, because of the high reactivity of its double bond, is readily
transformed into many useful products
Many materials originate from ethylene such as Ethanediol (antifreeze), ethanol,
dibromoethane (petrol additive), styrene to polystyrene, polyethylene, Vinyl chloride to
PVC. Ethylene reacts with other molecules by addition process, Hydrogenation (addition of
Hydrogen), Halogenation (addition of halogen gases, like chloride and bromine),
Hydrohalogenation (addition of HX molecules like HCl, HBr)
 Identify that ethylene serves as a monomer from which polymers are made
Monomer is compound with small molecules able to join together to form long chain
polymer molecule
Polymer is long chian molecules formed by joining monomer structures. Sometimes called
macromolecules.
Polymer chains often contain thousands of monomers. E.g. polyethylene generally has
10000-20000 ethylene molecules joined together. Ethylene is a monomer from which
polymers such as Polyethylene, Poly vinyl Chloride and Polystyrene are formed.
 Identify polyethylene as an addition polymer and explain the meaning of this term
Addition Polymerisation is where same double bonded monomers combine to form polymer
without loss of any atoms.
 Outline the steps in the production of polyethylene as an example of a
commercially and industrially important polymer
The production of polyethylene is a three step chain reaction.
1. Initiation
An unstable substance, usually organic peroxide is used to initiate the reaction. This is
because ethylene does not react with itself unless under pressure. The initiator will bond
with ethylene, breaking the double bond and the free electron migrates to the other end,
allowing that ethylene to become a free radical and react with other ethylene molecules to
form a long chain.
2. Propagation
Growing of the chains. The chain of ethylene grows until this free radical ethylene chain
combines with another free radical ethylene chain to form a complete polyethylene
molecule.
3. Termination
The combination of free radicals is called termination
High pressure produce branched polyethylene, low pressure produce unbranched
polyethylene
 Identify the following as commercially significant monomers:
–
Vinyl chloride (chloroethene)
–
Styrene (ethenylbenzene)
 Describe the uses of the polymers made from the above monomers in terms of
their properties
Polymer
Properties/Structure
Low Density Highly branched, the side branches disrupt
Polyethylene packing of polymer chains, therefore fewer
(LDPE)
crystalline regions.
Low Melting Point 80 degrees.
Soft, flexible (weak dispersion forces),
Transparent (less scattering and refraction of
light) and waxy surface, scratches easily.
Chemically inert, water proofing, electrical
insulation and good impact strength.
High
Density
Polyethylene
(HDPE)
Minimal side branching, linear polymer
backbone, chains closely packed together,
hence strong dispersion force, high
crystallinity therefore scatter refract light.
High density.
Melting Point 135 degrees
Hard, rigid, tough, very stiff. Can take high
pressures, slows corrosion Waxy surface and
translucent/white. High tensile Stength
Poly Vinyl Rigid, hard, brittle, electrical insulator, resists
Chloride
effects of weathering
(PVC)
Adding a plasticiser, soften PVC (decrease
dispersion force)
Adding a heat stabiliser (lead compound),
improves
its
resistance
to
head
decomposition
Adding a Flame retardant (auntimony(iii)
oxide) lowers its flammability (gives off
toxic corrosive HCl)
Adding a UV absorber (titanium oxide),
prevents UV decomposition of the plastic
when exposed to sunlight.
Polystyrene Versatile thermoplastic (no crosslinks or
(PS)
bonding between chain, can be remoulded or
recycled)
Crystal polystyrene
Clear amorphous polymers, very stiff, brittle,
good insulator, sparking clarity transparent,
can be moulded easily, low softening
Uses
Shopping
and
garbage
(plastic) bags.
Food Containers, packaging
for frozen food
Milk and fruit juice packs
Squeeze bottles
Electrical insulation
Cling wrap
Lining of cardboard milk
bottles
Bags
Gas pipes, agric pipes
Kitchen
containers
and
utensils (bowls, freezer bag)
Milk crates
Plastic furniture (bucket,
wheelie bins)
Car parts
Building material
House
walls,
window
components,
Electrical
conduit, credit card.
Flexible tubing, guttering,
upholstery covering, surgeon
gloves, shower curtains,
raincoat, toys.
Hot PVC water pipes
PVC outdoor products
Building panels (pigments
incorporated for colouring)
Food packaging, medical
care products (disposable),
drinking glasses, CD cases.
Plastic for heat-pressed food
packaging,
washing
machines, TV backing, hair
dryers.
temperature
Portable coolers, vacuum
Expanded polystyrene
flasks, foam packing, surf
White, has good heat, cold and sound boards, marker buoys, bike
insulation, low density, resists high impact
helmets.
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
The raw materials for making polymers come from crude oil. There is concern the world
will use up all its available oil reserves within the next few decades as the analysts predict.
Currently there is a pressure to reduce energy use and develop alternative fuels, because
1) Green house effect and damage to ozone layer
2) As supplies of oil diminish, cost will increase.
Petrochemical industry (mainly plastics) consumes 3 to 5% of the total oil used in the world
today, and, hence is less affected by the price rise
Different arguments are
Because oil supplies are going to run out in the foreseeable future, we should be developing
alternative sources of the raw materials for plastics.
As oil supplies diminish, costs will increase and oil will become too expensive to use as a
fuel. Alternative fuels will become cost effective. Petrochemical industry will be less
affected by price rises (the cost of raw material is smaller proportion of cost of finished
product) and thus can still afford to use oil. Hence remaining oil will be exclusive domain of
petrochemical industry and last for many more decades.
However it is still advisable to develop alternative sources of ethylene. Ethanol is the main
candidate for an alternative source of ethylene. Ethanol can be produced by fermentation
from a variety of agricultural crops, and cellulose is also a possible source of ethylene.

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
Biopol, PHB-PHV is a copolymer of consisting of two monomers, 3-hydroxybutyrate and
3-hydroxyvalerate. They can be produced from “Alcaligenes eutrophis” bacteria.
Alcaligenes eutrophis bacteria are grown in a high glucose high valeric acid, low nitrogen
environment. They are provided with a carbon based food source. They are fed appropriate
nutrients so it multiplies rapidly and grows into a large quantity. The polymer is then
isolated and purified.
The diet is changed, and nutrient restriction means that the bacteria no longer increases
production but instead begins to make desired polymer and stores it for later use as an
energy source (30-80% dry weight). This excess energy is stored in their cell walls as
granules of PHB-PHV
Hot liquid chloroform (CHCl3) is used to dissolve the copolymer and it is evaporated off to
leave biopol granules. The solid waster is removed by centrifuging, precipitating the PHB
from solution and drying the powder.
Properties
Biocompatible and biodegradable
Similar to polypropylene
Insoluble in water
Permeable to oxygen
Resistant to UV light, acids and bases
Soluble in chlorinated hydrocarbons
High melting point, high tensile strength,
more dense than water but non toxic
Uses
Disposable items such as razors, rubbish
bags, nappies, fast food utensils and paper
plate
Disposable plastic items such as shapoo
bottles and cosmetics
Injection moulded into plastic items that is
likely to be left in the environment such as
fishing lines, gold tees, ag pipes
Disposable hospital material and medical
supplies
However currently the biopolymer cost far more to produce than the crude oil based
polymers, and the production rate is too small.
Scientists are researching in different way to improve it. Genetical engineering allow
bacteria like Escherichia coli or plants like potatoes to grow biopolymer just like
Alcaligenes eutrophis, therefore has faster growth, better yields, easier recovery and
production of less waste biomass. Alternatively to allow Alcaligenes eutrophis produce
large quantity of biopolymer from inexpensive sources of carbon, hence lower the cost.
Since Biopolymers have the advantage of being biodegradable thus allowing better waste
management and they are being made from renewable sources, they hold great potential in
the future as crude oil based polymers are using precious fossil fuels that are going to be
used up soon.
 Explain what is meant by a condensation polymer
They are polymers that form by the elimination of a small molecule (often water) when
pairs of monomer molecules join together.
Each monomer has two identical functional groups
Reaction between the functional groups on each monomer
Releases a small molecular weight molecule
Generally slower than additional polymerisation. If two different monomers are present,
such polymers are often called copolymers.
 Describe the reaction involved when a condensation polymer is formed
Condensation polymers result in a by product that is commonly a small molecule. E.g. water
or hydroxide. For example, cellulose is a naturally occurring condensation polymer. The
monomer from which it forms is glucose. Polymerisation occurs by the elimination of water
molecules from between pairs of glucose molecules.
n (OH-C6H10O4-OH)  H - (O-C6H10O4) n – OH + (n-1) H2O
This is saying that n molecules of glucose combine to form one molecule of cellulose
(containing n glucose units) by eliminating (n-1) molecules of water

Describe the structure of cellulose and identify it as an example of a condensation
polymer found as a major component of biomass
Cellulose is a linear condensation polymer containing 1800-3000
beta glucose units per molecule. Cellulose is made from beta glucose,
which is when the hydroxyl group of the first carbon atom is on the
same side as the CH2OH group.
It has 5 carbon atoms and an oxygen atom forming a puckered ring.
There are OH groups on 5 of the C atoms.
For bonding to occur alternate glucose units must be inverted
This bonding produces a very linear molecule, caused by the geometry of the rings and the
C-O-C bond angle.
Bulky CH2OH groups are on alternate sides, creating a flat straight and rigid molecule
The number of hydroxyl groups facilitates hydrogen bonding, causing molecules to bond
side by side, resulting in the rigidity of the molecule
Long, strong cellulose fibres (wood) make good building material
Because hydroxyl groups are engaged in hydrogen bonding to adjacent molecules, there are
reduced hydroxyl groups to bond with water, very large bonded molecules are thus insoluble
in water
More resistant to chemical attack.
Biomass is organic matter, or material produced by living organisms. It is mainly plant
material, though the term also includes animal excreta and material made by algae.
Cellulose is the major component of biomass.
 Identify that cellulose contains the basic carbon-chain structures needed to build
petrochemicals and discuss its potential as a raw material
Each glucose unit of cellulose has five carbon atoms joined together in a chain, so it could
be regarded as a basic structure for making starting molecules for petrochemicals molecules
such as ethylene, propene and butene.
Plants produce far more cellulose than starch or other biopolymers, and thus there would be
great benefits if we could use cellulose as a source of materials we currently make from oil.
Bacteria can digest cellulose into glucose, and further ferment glucose into ethanol. The
ethanol can be dehydrated into ethylene, which is used to produce other polymers. Bacteria
in ruminants and intestines of termites produce enzymes to break down cellulose into
glucose monomers.
The fact that there is no simple or efficient chemical way currently of breaking cellulose
into glucose has been a stumbling block for using cellulose as a raw material for chemicals.
Biomass fuels currently cost more to produce than fossil fuels. Energy is needed to plant
tend and harvest crops
Arable land must be used to grow dedicated energy crops, reducing the land available for
food crops. Vast crops can alter local water table and demand for soil nutrients.
Cellulose is used for cotton, especially for textiles, paper and cardboard
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
Ethylene is made from ethanol by dehydration. This is a reaction that involves the removal
of water. The ethanol is heated with concentrated sulphuric or phosphoric acid, which acts
as a catalyst. It is needed in this reaction because ethanol itself will not decompose
spontaneously into ethylene and water upon heating.
C2H5OH (l)
Concentrated Acid

  
C2H4 (g) + H2O (l)

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
The reverse reaction, the addition of water to ethylene is called hydration. It too needs heat
and a catalyst which is generally dilute aqueous sulphuric acid. A catalyst is necessary,
because the water molecule is not reactive enough to attack the bonds of ethylene to form
ethanol.
C2H4 (g) + H2O (l)
DiluteAcid


C2H5OH (l)

Process information from secondary sources to summarise the processes involved
in the industrial production of ethanol from sugar cane
Sugar cane contains molasses, which contains sucrose. Sucrose C12H22O11 is hydrolysed to
form the isomers glucose C6H12O6 and fructose C6H12O6. Both glucose and fructose can be
fermented to carbon dioxide and ethanol
C12H22O11 (aq) +H2O (l) 
 C6H12O6 (aq) + C6H12O6 (aq)
Sucrose
C6H12O6 (aq)
Water
Glucose
Fructose
( zymase)
Yeast


 2C2H5OH (aq) + 2CO2 (g)
Glucose/Fructose
Ethanol
Carbon dioxide
 Describe and account for the many uses of ethanol as a solvent for polar and
non-polar substances
Ethanol is widely used as solvent in industry and home for cosmetics (perfumers,
deodorants, after shaves), food colouring and flavourings (cochineal, vanilla essence),
medicinal preparations (antiseptics) and some cleaning agents.
Ethanol is a good solvent because its alkyl group and hydroxyl group. In its hydroxyl group
the C-O and O-H bonds makes the molecule polar because O is more electronegative than C
or H and the function group form an angle. Like dissolve like, Ethanol is therefore a good
solvent for polar substances (salts) as ethanol can form dipole dipole force with them. The
hydroxyl group also form hydrogen bond with many other substances such as water, glucose
and some proteins, therefore ethanol is completely miscible in water.
The alkyl group is non polar and allows ethanol to act as a solvent for some non polar
substances including some hydrocarbons, oils and resins. It forms dispersion forces with
non polar substances.

Process information from secondary sources to summarise the use of ethanol as
an alternative car fuel, evaluating the success of current usage
Air pollution concerns led to introduction of cleaner burning fuels and renewable fuels or
fuel additive. Ethanol can be used as a petrol extender, while petrol containing 10-20%
ethanol (anhydrous) can be used in ordinary petrol engines without any modification, higher
percentage of ethanol (hydrous) require engine modification.
Brazil is the largest producer of ethanol in the world, in 1975 Brazil implemented biofuels
program and adopted ethanol as its major fuel for cars. It grew sugar cane specifically for
conversion to ethanol.
Political and economic pressures (expense) delayed implementation of biofuels program and
it was cancelled after a while, however it is picked up again due to its success. The outlook
is positive but program will proceed at slower rate.
USA, Canada and Australia use ethanol as extender (10-20%)

Outline the use of ethanol as a fuel and explain why it can be called a renewable
resource
Ethanol is often blended with petrol when used as a fuel. Ethanol burns cleaner than oil, and
less carbon is deposited in the engine. Spark plugs thus last longer. Ethanol has been
promoted as a fuel on the grounds that it is a renewable resource. It is made from carbon
dioxide, water and sunlight (carbohydrates) and when it is burnt it returns to carbon dioxide
and water, which can be reconverted to ethanol. Hence it is advocated also as a fuel that is
neutral with respect to the greenhouse effect. The carbon dioxide liberated when it burns is
that which was used in its synthesis. However fertilisation and distillation process require
much energy.
Obtained from molasses, the left over syrup from sugar milling.

Describe conditions under which fermentation of sugars is promoted
Fermentation is a process in which glucose or fructose is broken down into ethanol and
carbon dioxide by the action of enzymes present in yeast. It requires
Suitable grain or fruit which contain sugar mashed up with water
Yeast is added, Air is excluded (if oxygen is present, yeast will reproduce instead of
fermenting), Temperature around 37 and *Ethanol is continuously removed from it.

Summarise the chemistry of the fermentation process
Enzymes (biological catalysts) first convert any starch or sucrose in the mixture into glucose
and or fructose, then other enzymes convert glucose or fructose into ethanol and carbon
dioxide. Bubbles of carbon dioxide are slowly given off. Yeast can produce ethanol contents
up to about 15%. Alcohol concentrations above this kill the yeast and stop further
fermentation. Higher alcohol contents require distillation of the liquid.

Define the molar heat of combustion of a compound and calculate the value for
ethanol from first-hand data
The molar heat of combustion of a substance is the heat liberated when one mole of the
substance undergoes complete combustion with oxygen at a constant pressure of exact one
atmosphere with the final products being carbon dioxide gas and liquid water.
The enthalpy change is always energy absorbed. Since combustion is exothermic, it always
has a H sign that is negative.
Molar heat of combustion for ethanol
C2H5OH (l) + 3O2 (g) 
 2CO2 (g) + 3H2O (l) H =-1367 kJ/mol
Octane, petrol component
C8H18 (l) +
25
O2 (g) 
 8CO2 (g) + 9H2O (l) H =-5464 kJ/mol
2

Assess the potential of ethanol as an alternative fuel and discuss the advantages
and disadvantages of its use
Ethanol is a fuel that readily burns
C2H5OH (l) + 3O2 (g) 
 2CO2 (g) + 3H2O (l)
Advantage
Disadvantage
Renewable resource, avoid further use of Large areas of land required for production
non renewable fossil fuel which is running of raw materials. Less land for growth of
low at supply
crops. Also cause soil erosion, deforestation,
fertiliser run off and salinity
Reduce greenhouse gas emission
Contain oxygen therefore help to combust Disposal of smelly waste fermentation
more completely, reduce toxic emission such liquors after removal of ethanol would
as carbon monoxide and carbon to the present major environmental problems.
environment
Excellent solvent, deposits that have built up Does not release as much energy as petrol on
over time will be dissolved in ethanol, fuel complete combustion.
filters last longer, providing a cleaner system
Higher flash point, combust mixtures of Ethanol sources currently are less efficient
ethanol vapour are not as readily formed in than petrochemical fuels, cost more to
cold climates
produce
As fossil fuels are running out very soon, the cost of petrochemical fuels rises, and as
technology improve, scientists are researching for better, cheaper method of producing
ethanol, therefore ethanol holds great potential as an alternative fuel.
 Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8
1
2
3
4
5
6
7
8
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
a galvanic cell is produced
A displacement reaction is a reaction in which a metal converts the ion of another metal into
the neutral atom. One species of the reaction is oxidised whilst the other species is reduced
(one species donates electrons, whilst the other species gains these electrons). Active metals
will displace less active metal ions from solution: for example zinc will displace copper ions.
Zinc releases electrons from its outer shell and they are accepted by the copper ions in
solution displacing it from solution.
Oxidation is the loss of electrons (charge increases)
Reduction is the gain of electrons (charge decreases)
Types of redox reaction apart from metal displacement reaction
Metal/ non metal reactions
2Na(s) + Cl2  2Ag(s) + Cu2+(aq)
Metals reacting with dilute acids
Zn(s) + 2H+(aq)  Zn2+（aq）+ H2(g)
Active metals reacting with water
2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
Non metal displacement reactions
F2(g)+2Br-(aq)  2F-(aq) + Br2(l)

Identify the relationship between displacement of metal ions in solution by other
metals to the relative activity of metals
Of two metals, the more reactive metal is the one which will displace the other metal from a
solution of its ions. More active metals lose electrons more easily; become oxidised. Less
active metals are displaced from solution; become reduced

Account for changes in the oxidation state of species in terms of their loss or gain
of electrons
For positive monatomic ions the oxidation state is the charge on the ion. The oxidation
number is an arbitrary charge assigned to an atom.
An increase in oxidation state shows the atom has been oxidised
A decrease in oxidation state shows that the atom as been reduced
To determine the oxidation number:
Elements in elemental state: oxidation number = 0
Compounds of O: oxidation number = -2 except in peroxides = -1, F2O = +2
Monatomic ions: oxidation number = charge on ion (e.g. Cu2+=+2)
Compound of H: oxidation number = +1 (except metal hydrides = -1)
Polyatomic species: sum of oxidation numbers of all species equals charge on ion or
molecule

Describe and explain galvanic cells in terms of oxidation/reduction reactions
A galvanic cell or electrochemical cell is a cell where a spontaneous chemical reaction
occurs, converting chemical energy to electrical energy (producing current)
Strong oxidants generally contain an element in a high oxidation state (e.g. Cr2O72- is a
strong oxidant as Cr has a +6 oxidation state)
Strong reductants generally contain an element in a low oxidation state (e.g. active metals
such as K are strong reductants; 0 oxidation state)
The more active metal is oxidised at the anode, less active metal is reduced at cathode

Outline the construction of galvanic cells and trace the direction of electron flow
Redox reactions involve transfer of electrons from one reactant to another. An electric
current is a flow of electrons through a wire. Redox reactions can generate electricity by
arranging for the oxidation and reduction half reactions to occur at different locations, and
by providing a wire for the electrons to flow through.
Conductors of a cell connected to the external circuit are called electrodes. The electrodes
must be conductors, and may not be insulators.
The electrolyte is a substance which in solution or molten conducts electricity
Chemical reactions occurring at the electrodes are called electrode processes or electrode
reactions.
Salt bridge is essential for migration of ions and completing the circuit. The substances (ion)
in salt bridge should not react with any substances in the cells, nor form precipitate. KNO3
is a good choice.
– Anode: Electrode where oxidation occurs. Negatively charged, electrons are released
into the external circuit at the anode
– Cathode: Electrode where reduction occurs. Positively charged, electrons are
removed from the external circuit at the cathode.
– Electrodes: Conductors (metals or graphite) which are the interface between the
external and internal circuit. Electrodes can be reactive (e.g. Zn) or inert (e.g. Pt, C).
Reactions can also occur on the interface between electrode and electrolyte.
– Electrolyte: An aqueous solution containing free, mobile cations and anions.
Electrolytes exist in the anode and cathode compartments and the salt bridge.
Electrons cannot flow through an electrolyte.
– Salt bridge: constructed of a glass U-tube or a strip of filter paper. The salt bridge is
filled/ saturated with an inert electrolyte (e.g. KNO3). The salt bridge allows the
migration of ions between the anode and cathode compartments to maintain
electrical balance/neutrality.
– External circuit: composed of conductors where electrons can flow (electrodes,
–
–
–
–
–

connecting wires, voltmeter, ammeter, load)
Oxidant: The ion species in the cathode compartment, which becomes reduced. The
oxidant is located in the electrolyte.
Reductant: the ion species in the anode compartment which becomes oxidised.
Reductant can be in the electrolyte or the anode itself.
Standard Electrode Potential (Eo) is the potential of that electrode in its standard
state relative to the standard hydrogen electrode.
Electron flow: electrons flow from negative anode to positive cathode. Electrons
cannot flow through electrolyte.
Ion flow: Ions flow (migrate) slowly in the electrolyte solutions. Negative ions
(anions) flow towards anode compartment. Positive ions (cations) flow toward
cathode compartment.
Define the terms anode, cathode electrode and electrolyte to describe galvanic cells
A galvanic cell is a device that allows a spontaneous redox reaction to take place in such
way that chemical energy is converted to electrical energy. It consists of two half cells, each
containing an electrode in an electrolyte solution. Oxidation takes place in anode where
reduction in cathode.

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:
Battery
Lead-acid cell
Button cell
Chemistry
Anode: Pb
Anode: Powdered Zinc
Pb(s) + SO42-  PbSO4(s)+2eZn + 2OH-  ZnO + H2O + 2eCathode: Pb/PbO2
Cathode: Carbon and AgO
+
2PbO2(s)+ 4H +SO4 +2e  Ag2O(s)+H2O(l)+2e-  2Ag(s)+2OHPbSO4(s)+ 2H2O(l)
Electrolyte: Potassium hydroxide
Electrolyte: Sulfuric acid
1.5V
2.2V
Cost and practicality Expensive, Suitable for cars and Ag cells are expensive, but small
trucks, relatively bulky and size and light weight with
heavy.
relatively large voltage
Robust and Reliable, long life, a They are used in watches,
storage battery, provides a large calculators,
cameras,
heart
burst of current to start engine. pacemakers, hearing aids.
Rechargeable. Work in wide High current and maintain stable
range of temperatures
voltage
Impact on society
Allowed the development of Allowed the powering of small
starters in cars and trucker, equipment
such
as
heat
efficient means of transport.
pacemakers, and hearing aids,
Important for charge storage in extending
human
life and
remote regions. Can store solar improved the standard of life
energy when connected to solar
Environmental
impact
panels
Explosive hydrogen gas is
released on recharging
Corrosive acid can pollute the
environment if spillages occur
Lead is toxic and electrodes and
casing must be recycled
Expensive silver needs to be
recycled
KOH electrolyte is caustic
No highly toxic materials that will
harm the environment
5. Nuclear chemistry provides a range of materials

Distinguish between stable and radioactive isotopes and describe the conditions
under which a nucleus is unstable
Isotopes are atoms that have the same atomic numbers but different mass numbers.
Radioisotopes are the isotopes that are unstable, radioactive and actively emit alpha, beta or
gamma radiation.
Stable isotopes are not radioactive, they all have atomic numbers less than or equal to 83
and a ratio of neutrons to protons between 1:1 to 3:2.
Unstable isotopes are radioactive. Any atoms with an atomic number greater than 83 are
unstable because the atoms are too large and the nuclear force is not strong enough to
withdraw the repulsive force of protons. If the ratio of neutrons to protons is less than 1:1 or
greater than 3:2, or outside the “zone of stability” in the graph below, then the atoms are
unstable isotopes. The nucleus of unstable isotopes has excessive energy therefore it
decomposes and undergoes radiate emission to reach ground state by releasing the excess
energy.
There are three type so radiation
 alpha particles = helium nucleus =
 beta particles = electrons =
0
1
4
2
He emits by most heavy elements
e emits by lighter elements
 gamma rays = electromagnetic radiation, always accompany either alpha or beta
emissions
x
y
E
Where E is the element, x is mass number which equal to proton + neutron and y is the
atomic number equal to proton

Describe how transuranic elements are produced
In 1940 Neptunium, the first Transuranic element (elements have atomic number greater
than 92, uranium) was created by Edwin Mattison McMillan’s team. It was produced by
bombarding Uranium 238 with a neutron slowly, forming unstable Uranium 239 and
Uranium 239 then decay into Neptunium 239 and beta particle.
238
92
u +
1
0
n 
239
92
u 
239
93
Np +
0
1
e
Plutonium was produced by bombarding uranium with deuteron at a very high speed,
accelerating by the 60-inch cyclotron. It first formed neptunium 238, and then decayed into
Plutonium by beta emission.
238
92
u +
2
1
H

238
1
Np + 2 n
93
0
238
93
Np 
238
94
Pu +
0
1
e
Transuranic elements do not exist in nature. Uranium is the last natural element. The first
few of these artificial radioisotopes are produced by bombarding the nuclei of an element by
substances such as neutrons, alpha particles or deuteron (nuclei of heavy hydrogen) slowly
or in particle accelerator.

Describe how commercial radioisotopes are produced
Commercial radioisotopes are the radioisotopes that are industrially produced and massively
employed in different areas which have commercial value. For example Technetium 99m
was widely employed in medicine graphic imaging of the body and Americium 241 is
industrially produced and used in smoke detectors
They can be produced in an accelerator which will produce neutron deficient isotopes
(isotopes have extra protons) or a nuclear reactor which will produce neutron rich isotopes
(isotopes have extra neutrons)
Particle accelerators such as cyclotrons will accelerate light ions such as protons, deuterons,
helium 3 ions and alpha particles to very high speeds (close to speed of light), producing an
intense high energy beams of the above ions, which then is used to bombard at nuclei of
atoms, the repulsive force between the ions and the nuclei of atoms will be overcame by the
very high speed.
In a nuclear reactor, target nuclei are placed in the reactor core. Neutrons are used to
bombard the target, producing neutron rich isotopes. Control rods inside the reactor absorb
the extra neutrons to control the uranium chain reaction, making sure it is safe and releasing
neutrons at a slow and controlled rate. For example Cobalt 60 was made by putting stainless
steel rods containing pellets of Cobalt 59 into the reactor and releases a neutron into it.
59
27
Co +

1
0
n 
60
27
Co
Process information from secondary sources to describe recent discoveries of
elements
Ununhexium (Uuh) atomic number 116 is discovered on July 19, 2000, scientists at Dubna
(FLNR) detected a single decay from an atom of ununhexium following the irradiation of a
Cm-248 target with Ca-48 ions. It is very short lived (47 milliseconds) and decomposes to a
known isotope of element 114. Four isotopes are currently known with masses 290-293.
The most stable is Uuh-293 with a half-life of 63 ms.
248
96
Cm +

48
20
Ca 
292
1
Uuh + 4 n
116
0
Identify instruments and processes that can be used to detect radiation
Photographic film: darkening of the film
Geiger-Muller tube and counter: Ionising properties of radiation, good for beta
Cloud Chamber: consist cold super saturated vapour and they condense on ions
Scintillation counter or detector: Photoelectric effect, emitting flash of light

Identify one use of a named radioisotope:

Describe the way in which the above named industrial and medical radioisotopes
are used and explain their use in terms of their chemical properties
-in industry Cobalt-60
Cobalt 60 can be used in industrial radiography. When materials are manufactured, a
radioactive source is placed in one side while the detector is placed at the other side. The
amount of radiation received by the detector depends on the thickness of the material, when
the thickness of the material being manufactured changes the signal will differ, sending this
information back to the control to optimise the manufacturing process. Cobalt has low
energy emission and most of them are absorbed by manufacturing materials, hence
minimise the danger of radiation, it also has a longer half life of 5.3 years, therefore factory
don’t need to replace it frequently. It is also used to irradiate food, destroying insects,
bacteria and micro organisms.
-in medicine Technetium 99m
Technetium 99m is used in gamma ray imaging of human organs. It can be injected into
bloodstream and can detect blood clots, constrictions and other circulation disorders or
attached to tin compound, chemically bound to red blood cell and becomes a tracer. It only
emits low energy gamma rays which cause little damage to the body but are easily detected
by gamma sensitive cameras. It has a half life of 6 hours, long enough to investigate the
body but also short enough to minimise potential damage. It also has a number of oxidation
states therefore it can be chemically bonded to different elements that different organs of the
body absorb and can target a range of specific organs or tissues.

Use available evidence to analyse benefits and problems associated with the use of
radioactive isotopes in identified industries and medicine
Medicine:
Use of radioisotopes in medical imaging such as Tn 99m has allowed more effective and
accurate diagnosis of diseases and has resulted in a reduced need for open surgery. This has
numerous human benefits and decreases recovery time for patients, and reduces trauma that
could arise from open surgery. However the nature of radioactive isotopes may become
dangerous to operators and patients. Exposure could result in diseases and in some cases,
cancer. Tn 99m has short half life, which is good for patient but it also means that it needs to
be produced on site.
Industry
Use of radioisotopes in food irradiation destroy bacteria and mould, make food safe and
keep it fresh longer, reducing the wastage. However it won’t necessarily kill all dangerous
organisms and it destroys some vitamin content in food. It also leads to formation of
harmful compound and laxity with food hygiene standards
Food irradiation need gamma rays of sufficient energy to destroy bacteria, but cannot be
enough energy to make food radioactive, source must have a reasonably long half life such
as Cs-137 with 30 years and Co-60 with 5.3 years