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SYLLABUS DOT
POINTS:
CHEMISTRY
PRODUCTION OF MATERIALS
THE ACIDIC ENVIRONMENT
CHEMICAL MONITORING AND
MANAGEMENT
OPTION – SHIPWRECKS, CORROSION
AND CONSERVATION

PRODUCTION OF
MATERIALS:
1
...
Some scientists research the extraction of materials from biomass to
reduce our dependence on fossil fuels
3
...
Oxidation-reduction reactions are increasingly important as a source of
energy
5
...
Fossil fuels provide both energy and raw materials such as
ethylene, for the production of other substances
Students learn to:
• construct word and balanced formulae equations of chemical
reactions as they are encountered
• identify the industrial source of ethylene from the cracking of
some of the fractions from the refining of petroleum
Petroleum is a mixture of hydrocarbons (liquid crude oil and natural
gas), which can be separated into various compounds to create simpler
molecules such as ethylene
...
Cracking the molecules
can be done by heating the fractions at very high temperatures (thermal
cracking)
...
Catalysts allow cracking to occur at relatively lower
temperatures (catalytic cracking), the heat and catalyst used determines
the product obtained from cracking
...
g
...
The double bond in
ethylene allows it to easily react with other molecules and makes it a
useful starting point for producing other compounds
...
The addition of water to ethylene
produces ethanol; industrially produced by absorbing ethylene in
concentrated sulphuric acid, then hydrolysed by diluting with water, or
converted by direct catalytic hydration (ethylene and steam passed
over a solid phosphoric catalyst)
...

e
...
addition of water to ethylene
Ethylene (C2H4)

• identify that ethylene serves as a monomer from which
polymers are made
A monomer is a small molecule, many of which can be joined together
to form a long chain molecule called a polymer
...
This process is called
polymerisation
...
Polyethylene is an example on
an addition polymer as it is formed from the addition reaction of
ethylene monomers
...
By the addition of more ethylene molecules to the open carbon
atoms, a polymer known as polyethylene is formed
...
LDPE uses
temperatures between 80º and 300º and very high pressures with
oxygen or an organic peroxide initiating the reaction
...
LDPE is a branched polymer as branched molecules cannot
be packed together tightly, so they tend to be less dense than HDPE
...
The stages in the production of polyethylene (LDPE and
HDPE) are:
1
...


2
...
Termination – when free radical ethylene chains combine, a
complete polyethylene molecule is formed and the process stops

LDPE has a low
melting point, is
soft, tough,
flexible, translucent and of generally high purity, making it readily
melted and moulded, and thus suitable for flexible film wrap,
sandwich bags, plastic bags and plastic squeeze bottles
HDPE is crystalline, making it rigid, with a higher melting point, it is
chemically resistant, so it is useful for petrol tanks, rubbish bins,
plastic crates, and agricultural piping
...
Its systematic name is
chloroethylene and polymerisation of this monomer results in
polyvinylchloride or PVC

– styrene
By replacing one of the hydrogens in ethylene (C2H4), with a
benzene ring (C6H6) – actually a benzene ring minus a hydrogen atom
making it a phenyl group (C6H5) – styrene is made
...
Additives can also be added to
alter its flexibility and to resist degradation by UV rays
...
This makes it suitable for the
use of containers, wrapping film, blister packaging, vegetable oil
bottles, electrical insulation, pipes/hoses, flooring, outdoor
furniture, videos and credit cards
...
It is durable (keeps it shape), it is a good insulator, is light
weight (because of its low density), and its shape can be moulded to
protect products
...
This makes it suitable for the
uses of fruit boxes, clothes hangers, packing foam, egg cartons,
meat trays, CD’s, plastic cutlery, toys, surfboards and hot drink
cups (Styrofoam)

Students:
• gather and present information from first-hand or secondary
sources to write equations to represent all chemical reactions
encountered in the HSC course
• identify data, plan and perform a first-hand investigation to
compare the reactivities of appropriate alkenes with the
corresponding alkanes in bromine water
EXPERIMENT: comparing reactivities of alkenes and corresponding
alkanes
AIM: to examine the reactions of alkanes and alkenes with bromine
(bromine water)
MATERIALS:
- bromine water
- test tubes
- alkane (cyclohexane)
- alkene (cyclohexene)
- fume cupboard
INTRODUCTION:
Alkanes are saturated substances as they have all single bonds filled
with the maximum number of atoms/molecules, whereas alkenes are
unsaturated substances as they have a double bond rather than the
maximum amount of atoms/molecules
...
When the
alkane and alkene is reacted with bromine water, which is naturally
brownish in colour, one visible reaction will take place
...

RISK ASSESSMENT:
- the vapour of bromine water is poisonous to humans, the fumes are
dangerous for our lungs, so the experiment must take place under a
fume cupboard
- hydrocarbons are very volatile, so the lab in which the experiment is
done must be free from any naked flames
METHOD:
1
...
Shake vigorously and observe
3
...
Shake vigorously and observe

RESULTS:
- one test tube became discoloured and one remained the
yellow/brownish colour of the bromine water

• analyses information from secondary sources such as computer
simulations, molecular model kits or multimedia resources to
model the polymerisation process

2
...
We are dependent on
petroleum for 80% of our transport needs, and as more countries
become industrialised and the population grows, that need for
petroleum will keep increasing, also resulting in a significant increase
in price
...
For us to
continue to live our lifestyle, we need to find alternative options for
fossil fuels such as petroleum
...
g
...
Cellulose is
extracted from these natural materials, as it is a major carbohydrate in
all of them
...
From ethanol, ethylene can also be
produced
...
The process of producing products from biomass is
currently more expensive than current process involving
petrochemicals, but as techniques for alternative sources are improved
and fossil fuels continue to deplete, costs will decrease
...
As they are being
formed they release a small molecules such as H2O (thus the name
condensation)
...
Some examples of condensation polymers include
polyesters and polyamides (nylon)

• describe the reaction involved when a condensation polymer is
formed
The formation of a condensation polymer involves the monomers
(either the same or different) joining together and releasing a small
molecule, such as water in the process, thus the name ‘condensation’
...


• 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 natural polymer made by linking together smaller sugar
units of a form of glucose (β-glucose)
...
Β-glucose serves as the
monomer from which cellulose is formed, it is a monosaccharide or
‘single sugar’
...
Linking more β-glucose sugars creates
cellulose, a polysaccharide
...
There are many –OH groups around the β-glucose ring,
readily forming hydrogen bonds with –OH groups from neighbouring
chains
...


• identify that cellulose contains the basic carbon-chain
structures needed to build petrochemicals and discuss its
potential as a raw material
Cellulose being a natural polymer, is also useful as a raw material for
various uses
...
Humans lack the necessary enzymes to
digest cellulose, but other animals such as termites have the ability to
break down cellulose and use it as a food
...
To make
paper it is necessary to treat the wood pulp with alkalis to break down
this lignin so that the pulp can be pressed into a matte of compressed
cellulose fibres
...
Cellulose has the potential to be used in
manufacturing plastics, as oil is currently used for this purpose, and its
dwindling supply needs to be addressed
...
As it is plentiful in plants and biomass, it would be
considered a renewable resource
...


Students:
• use available evidence to gather and present data from
secondary sources and analyse progress in the recent
development and use of a named biopolymer
...
It is a copolymer as it is made up of two monomers,
polyhydroxybutyrate (PHB) and polyhyroxyvalerate (PHV)
...

Biopol is industrially produced by bacteria growing in tanks with a
carbon based food source, the polymer is then isolated and purified
...
Scientists have been attempting to find ways to
produce Biopol more economically, using genetic engineering
techniques
...
coli so that they
can produce Biopol too
...
coli can be used to produce this polymer,
but with faster growth, better yields, easier recovery, and the
production of less waste biomass
...

The properties of Biopol are very similar to that of polypropylene; it is
insoluble in water, permeable to oxygen, resistant to UV light, acids
and bases, soluble in chlorinated hydrocarbons, biocompatible and
biodegradable
...

There are many current uses for Biopol and many more potential uses
for it in the future
...
The fact that Biopol is biodegradable, makes
it very useful in our current society as the issue of landfills and waste
management is major
...
It is
expected that through research, scientists will be able to create
methods of producing Biopol at lower costs
...

Biopol has very strong potential to replace products made from fossil
fuels, and as technology and research improves, there will be ways in
which its potential can be fully experienced
...
Other resources, such as ethanol, are readily available from
renewable resources such as plants
Students learn to:
• describe the dehydration of ethanol to ethylene and identify the
need for a catalyst in this process and the catalyst used
Dehydration is the process of removing water from a molecule
...
The reaction is:
CH3CH2OH à CH2CH2 + H2O

Concentrated sulphuric acid is used as both a dehydrating agent and as
a catalyst
...
Another (commercial) way of
extracting water from ethanol, is to pass the ethanol vapours over hot
aluminium oxide, or to use a zeolite catalyst
...

These highly reactive sites attack the –OH on the ethanol and remove
it to form water, leaving CH3CH2+ behind as an ion
...
The double bond
in ethylene (ethene), allows for a reaction with water to take place
...
When the mixtures are diluted with water,
the sulfates hydrolyse to ethanol:
H2C=CH2 + H2SO4 à CH3CH2SO4H (ethyl hydrogen sulfate)
CH3CH2SO4H + H2C=CH2 à (CH3CH2)2SO4 (diethyl sulfate)
diluted with water
CH3CH2SO4H + H2O à CH3CH2OH + H2SO4
(CH3CH2)2SO4 + 2H2O à 2CH3CH2OH + H2SO4

• describe and account for the many uses of ethanol as a solvent
for polar and non-polar substances
The ethanol molecule works as a solvent on both polar and non-polar
substances as it contains both a polar and non-polar end
...
Hydrogen bonds can also form between oxygen and
hydrogen atoms (in ethanol), with water
...
These properties of ethanol, as well as
its low toxicity to humans, allow it to be used industrially as a solvent
...


• outline the use of ethanol as a fuel and explain why it can be
called a renewable resource
Ethanol is a cleaner alternative for fuel, when it is burnt in oxygen, it
undergoes complete combustion, releasing carbon dioxide and water
...
The combustion of
ethanol also releases a fair amount of energy
...
Unlike petrol,
ethanol can be considered a renewable resource because of the fact that
it can be made from plant material, and the products of its combustion
(carbon dioxide and water) are the reactants needed by plants for
photosynthesis
...


• describe conditions under which fermentation of sugars is
promoted
The conditions that promote the fermentation of sugar (glucose) are:
- anaerobic conditions (low amounts of oxygen, as too much
oxygen with turn ethanol acidic)
- 30-40ºC (warm enough for reaction to take place without killing
bacteria)
- water
- an enzyme/catalyst (an enzyme is essentially an organic catalyst,
generally zyamase which is produced from yeast)
- a small amount of yeast nutrients (such as phosphate salt)
- continual removal of ethanol (concentration of 14-15% alcohol
will kill yeast)

• summarise the chemistry of the fermentation process
The physical process of fermentation is:
1
...
filter to separate the remaining solid residue of cellulose, and
hydrolyse this solid residue with more acid until it is broken down
into sugars
3
...
ferment the sugar solution, using yeast or bacteria, to produce an
ethanol mixture and carbon dioxide, and distill to separate the
ethanol from the mixture

• define the molar heat of combustion of a compound and
calculate the value for ethanol from first-hand data
The molar heat of combustion is the amount of heat released by the
complete combustion of one mole of a substance
...
Thus value (the
amount of heat generated during complete combustion) is ethanol’s
molar heat of combustion
CH3CH2OH + 3O2 à 2CO2 + 3H2O ∆cH = -1367kJ/mol
*the minus sign indicates that heat is released (exothermic)
The molar heat of combustion can be determines experimentally by
calorimetry
...
The
temperature change of the second body is used to determine the molar
heat of combustion of the fuel
...
measure 150mL of water into the flask (water, 1mL = 1g)

2
...
fill the spirit burner with ethanol and weigh the burner and alcohol
4
...
light the wick and allow water to heat
6
...
record the final temperature reading
8
...
39 g of ethanol raised the temperature of the water by 58ºC
The molar weight of ethanol is 46
...
39 g of ethanol
represents 1
...
0 = 0
...
184 JK-1g-1
...
184 JK-1g-1 X 150g X 58ºC = 36400
...
4 kJ
As 0
...
4 kJ of heat, the molar heat of
combustion is:
364
...
0302 = 1205 kJ/mol
DISCUSSION:
In this experiment, it is assumed that the energy produced by the
burning ethanol went completely into raising the temperature of water
...
The molar heat of combustion from this experiment is 162 kJ
lower than the figure 1367 kJ/mol
...
91
35
...
39

• assess the potential of ethanol as an alternative fuel and discuss
the advantages and disadvantages of its use
Advantages of ethanol
Disadvantages of ethanol
• a renewable resource
• large areas of land
required for production
• can be produced from
of raw materials
agricultural wastes
• high cost of distillation
• reduction of greenhouse
gases
• high cost of removing
water from fuel (to
• reduction of carbon
prevent problems with
monoxide (combustion of
the carburettor, fuel
ethanol is complete)
injection systems and
• reduction of high-octane
corrosion of fuel lines)
additives (used to replace
• engines need to be
tetraethyl lead in petrol)
modified to take high
• spills are easily
percentages of ethanol
biodegraded or dilutes to
• during combustion other
non-toxic concentrations
volatile organic
• burns more cleanly
compounds are produced
(complete combustion)
that must be removed by
catalytic converters in
the exhaust system of a
vehicle
• spills are difficult to
contain and recover as
they blend with water
• lower energy value than
petrol (lower fuel
economy)
Currently, ethanol being used as a fuel is not a viable solution for
petrol
...

There are many issues currently surrounding the production costs,
energy required for production, and compatibility in cars, but as these
solutions are found, ethanol would be a very appropriate replacement
for petrol
...
An isomer is a compound having
the same molecular formula but different structures
...
E
...
C4H9OH (butanol)
Structual formula

Condensed structural formula CH3CH2CH2CH2O
H

CH3CH2CHOHCH3

Name

2-butanol

1-butanol

Students:
• 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
•

process information from secondary sources to summarise the
processes involved in the industrial production of ethanol from
sugar cane
E
...
Brazil grows sugar cane to be processed into ethanol for use in
vehicles
...
The vapour rises into the neck where it cools and
condenses into pure liquid ethanol with the impurities left behind in
the still
- Ethanol trickles down the condensing tube into a barrel

•

process information from secondary sources to summarise the
use of ethanol as an alternative car fuel, evaluating the success
of current usage
Any alkanol has the potential to be used as a fuel, but ethanol and
methanol are the cheapest
...
Ethanol burns more
completely, produces 80-90% fewer CO emissions, produces no soot
or sulphur oxides, and produces lower quantities of nitrogen oxides
...
Ethanol degrades some plastic and rubber
parts of fuel delivery systems, so standard vehicles would require
modification
...
Australia, for
example has tried a 10% ethanol blend in petrol to slightly lower the
demand for petroleum
...
Brazil is
evidence of the positive outcomes of using ethanol over petroleum
...
There were initial problems, but they
are now reaping the rewards as ethanol is half the price of petroleum
...


•

solve problems, plan and perform a first-hand investigation to
carry out the fermentation of glucose and monitor mass
changes
EXPERIMENT: Fermentation of Glucose
AIM: To monitor the mass changes in the fermentation of glucose
EQUIPMENT:
- glucose (20g)
- beaker
- hot plate
- scales
- yeast (5g)
METHOD:
1
...
Add 5g of yeast
3
...
Weigh the beaker and mixture
5
...
After 2 hours reweigh the beaker
7
...
07
658
...
92
626
...
24

C – D = water loss
A – B = total mass loss
A
B
C
D

CALCULATIONS:
658
...
92 = 2
...
83 – 626
...
59 (total water loss)
2
...
59 = 1
...
83/(12
...
04158145876 (moles of CO2)
m = V/VM
V = m x VM
V(CO2) = 0
...
79 = 1
...
022 mol (moles of glucose)
m(C6H12O6) = 0
...
74 g (mass of glucose)

•

present information from secondary sources by writing a
balanced equation for the fermentation of glucose to ethanol

•

identify data sources, choose resources and perform a firsthand investigation to determine and compare heats of
combustion of at least three liquid alkanols per gram and per
mole
EXPERIMENT: Heat of Combustion
AIM: to compare the heat of combustion of 3 alkanols
EQUIPMENT:
- aluminium can
- water
- spirit burner
- scales
- thermometer
METHOD:
1
...
Measure out 200mL of water and place in the cane
3
...
Weigh the spirit burner
5
...
Put the cap on the spirit burner
7
...
25
236
...
18 x 20
= 16720 J = 16
...
22 / 32
...
3189563698 mol
∆H = Q/n
= 16
...
3189563698 = 52
...

To improve the accuracy of this experiment we would need a better
source of combustion rather than a spirit burner so as to make
complete combustion, and to reduce heat loss to the atmosphere
...
Oxidation-reduction reactions are increasingly important as
a source of energy
Students learn to:
• explain the displacement of metals from solution in terms of
transfer of electrons
More active metals will displace less active metal ions from solution in
an oxidation-reduction reaction
...
In a displacement
reaction; the more active element changes from an element to an ion as
it loses/gains electrons, and the less active element changes from an
ion to element as it too loses/gains electrons
...

E
...
a coil of copper wire is dipped into a solution of colourless silver
nitrate, the shiny coat of copper disappears, turning to black, the
solution takes on a bluish hue and the black deposit turns to a silvery
colour (metallic silver is depositing on the copper and at the same time
copper is going into the solution)
- the more active element changes from an element to an ion:
Cu à Cu2+ + 2e- (oxidation half reaction)
- the less active element changes from an ion to an element:
Ag+ + e- à Ag (reduction half reaction)
2Ag+(aq) + Cu(s) à H2 (g) + Mg2+(aq) (overall reaction)

• identify the relationship between displacement of metal ions in
solution by other metals to the relative activity of metals
Activity series of metals:
K Na Li Ba Sr Ca Mg Al Zn Fe Co Ni Sn Pb (H) Cu Hg Pt Au
decreasing activity à
The list of activity series of metal is produced in order of decreasing
activity
...
(the more reactive metal displaces other metal from solution)
...
The further apart the two metals in the activity series,
the more vigorous the reaction
...

The higher that the metal is in the activity series, the greater the
amount of heat that is produced
...

E
...
2Ag+(aq) + Cu(s) à 2Ag(s) + Cu2+(aq):

- the silver ion is being reduced to silver metal
- the copper metal is being oxidised to the copper ion
- the silver ion is called the oxidant/oxidising agent as it accepts
electrons and causes the other species to be oxidised
- the copper metal is called the reductant/reducing agent as it donated
electrons and causes the other species to be reduced

• account for changes in the oxidation state of species in terms of
their loss or gain of electrons
Oxidation states/numbers are worked out from the following rules:
- The oxidation number of an atom in an elementary substance is zero
e
...
in Cl2 the oxidation number is zero
- The oxidation number of elements in a compound composed of ions
are the charges on those ions
e
...
+I -I +II -I
Na+ Cl- Mg2+ Br- in a neutral molecule the algebraic sum of the individual oxidation
numbers is zero
e
...
in water: +I -II 2 x (+I) + (-II) = 0
(H2O) H O
- In an ion the algebraic sum of the oxidation numbers is the charge on
the ion
e
...
in the carbonate ion: +IV -II (+4) +3 x (-2) = -2
(CO32-) C O
- Hydrogen has a charge of +1 when combined with non-metals (e
...

in H2S) and -1 when combined with metals (e
...
in NaH)
- Oxygen in compounds has a charge of -2 in oxides and -1 in
peroxides

• describe and explain galvanic cells in terms of
oxidation/reduction reactions
The galvanic cell consists of two half cells, and electrode in an
electrolyte solution
...
The electrode where oxidation
occurs is the anode and the electrode where reduction occurs is the
cathode
...
The choice of substance for the salt bridge must be such that is
does not react with any ions in the solution
...
This arrangement ensures that electrons cannot
go directly from the reductant to the oxidant, but they will move
through the external circuit
...
The
larger the galvanic cell, the more chemical energy is stored, and the
more electrical energy can be obtained from that cell

• outline the construction of galvanic cells and trace the direction
of electron flow
If a reaction between a certain metal and solution is exothermic
(releases heat), it is possible to have the electrons transferred through
an external circuit so that electricity can be produced (galvanic cell)
...
A wire connected to
the two electrodes allows the flow electrons, whereas the electric
charge in the solutions must be in the form of ions
...
Without a salt bridge, one half-cell would acquire
excess ions and a net positive charge, while the other would have a
deficiency of ions and a net negative charge
...
The reading on the voltmeter in the
electrical circuit, represents the potential difference between the two
half-cells, it is essentially the ’driving force’ for electrons
...
Oxidation takes part in one half-cell and reduction
takes place in the other
...

And electrode is an electrical conductor where electrons flow out of or
into half cells
...
Electricity can flow
through electrolytes by the movement of charged ions rather than
electrons
...
g
...
36 V
Mg(s) à Mg2+ + 2e2
...
35 V
Overall:
Mg(s) + Cu2+ à Mg2+ + Cu(s)

2
...
g
...
66 V
Al(s) à Al3+ + 3e1
...
23 V

* electrons don’t balance *
2Al à 2Al3+ + 6e2Ni2+ +6e- à 3Ni(s)

1
...
23 V

Overall:
3Ni2+ + 2Al(s) à 3Ni(s) + 2Al3+

1
...
g
...
76 V
Reduction: Ag+ + e- à Ag(s)
0
...
56 V

• 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:
– fuel cell
in terms of:
– chemistry
– cost and practicality
– impact on society
– environmental impact
- lead-acid cell:
The lead-acid battery is an example of a rechargeable battery that is in
widespread use
...
In the cell, the anode is a porous lead plate, while the cathode
is coated with lead dioxide
...
The reactions are:
Anode:
Pb(s) + SO42-(aq) à PbSO4 + 2eCathode:
PbO2(s) + 4H+(aq) + SO42-(s) + 2e- à PbSO4(s) + 2H2O(l)
When the car is running the battery is continually recharging
...
These batteries have the benefit of producing a constant
2V and can supply this current for short periods of time, and are
reasonable in price
...

-fuel cell:
Unlike batteries, fuel cells convert energy from chemical reactions
directly and continuously into electrical energy
...
The electrodes
in a fuel cell also do not undergo a permanent chemical change
...
For a fuel cell to work, the
electrodes must keep the fuel and oxidising agents separate, permit
contact between reactants and electrolyte, act as a catalyst for electrode
reactions, and conduct electrons
...
The process is relatively clean, quiet and efficient as
it is an electrochemical process
...
The disadvantage for a
fuel cell is in developing the electrodes so that they can handle the
reactions fairly quickly
...
There is now the
issue surround the disposal of them
...

Some batteries such as lead-acid cells can be recycled for lead
components but recycling for others in currently impractical

5
...
Isotopes of
elements can be written in different ways
...
g
...
All carbon atoms have an atomic
number of 6 so to figure out the number of protons: 12 – 6 = 6
...
The stability of an isotope depends on the makeup of its nucleus
...
These types are
radioactive isotopes or radioisotopes
...
5:1
...

E
...
cadmium decays emitting an alpha particle and changing into
palladium
114
110
4
48Cd à
46Pd + 2He
E
...
carbon-14 decays to nitrogen-14 and a beta particle
14
14
0
6C à 7N + -1e
E
...
when a neutron bombards bromine-79 it turns it to bromine-80, it
then releases this excess energy by gamma ray emission
80
80
35Br à 35Br + γ

• describe how transuranic elements are produced
Transuranic elements are those that have a larger atomic number than
uranium (Z > 92), they do not exist naturally in nature
...
When a neutron bombards uranium-238 it forms a
new element (neptunium)
...


Scientists have been able to produce two dozen transuranic elements
this way
...


• describe how commercial radioisotopes are produced
There are around 50 naturally occurring radioisotopes, and scientists
have produced another several thousands
...
Some of them are naturally occurring but it is
uneconomic to extract them from their ores where they are found in
small quantities
...
All
types of reactors produce neutrons, fissionable materials and heat
...

Cyclotrons:
Radioisotopes can be produced by cyclotrons, an electromagnetic
device that contains no uranium-bearing fuel elements and produces no
highly radioactive waste products
...
The
magnetic field keeps the particles moving in a spiral path, and when
very high speeds are achieved the positive particles collide with atoms
of the target substance
...


• identify instruments and processes that can be used to detect
radiation
Geiger Müller Counter: a wire anode runs along the axis of a metal
cylinder that is sealed at either end and contains a mixture of argon or
neon and methane
...
Radiation that
enters through a small window ionise the gas, which then allows a
spark to jump across the electrodes
...

Scintillation Counter: a brief localised light flash is produced when
ionising radiation is incident on it, the flashes can be electronically
converted to electric pulsed by a photomultiplier and counted
Cloud Chamber: a cloud chamber contains a supersaturated alcohol
solution which is mostly vapour, as the radiation passes through, it
ionises the gas and alcohol droplets appear as a mist around the ionised
droplets
...

Photographic Film: Radiation can expose photographic film, when the
film is processed the amount of darkening visible is an indication of
radiation the film has been exposed to
...
Radiocarbon dating is also used to determine the age of any
material containing carbon

–

in medicine
Technetium-99m can be used as a liver-bile tracer to determine the
functioning of the bile duct
...


• describe the way in which the above named industrial and
medical radioisotopes are used and explain their use in terms of
their properties
Carbon-14: has a half-life of 5730 years
...
This means that it emits 14 beta rays per
minute, so the radioactivity of carbon-14 is an indication of the time
that the water was last in contact with the atmosphere
...
In a similar way, radiocarbon dating can be used to
determine the age of any material containing carbon
...
Carbon-14 forms in such quantities such that their rate
of production equals their rate of decay, meaning there are constant
quantities in the atmosphere and constant concentration of these
substances in all systems that interact with the atmosphere
...
If technetium-99m appears
in the bile duct then it is normal, if there is no activity then the test is
ambiguous; either the bile duct is not working properly or the patient
has a liver that functions so slowly that the technetium-99m has
decayed before reaching the bile duct
...


Students:
• process information from secondary sources to describe recent
discoveries of elements
There are no more naturally occurring elements left to be discovered
...
They are all radioactive and many exist
for only a short period of time
...
The first element to
exist only in a laboratory was technetium, in 1937
...


• use available evidence to analyse benefits and problems
associated with the use of radioactive isotopes in identified
industries and medicine
Radioisotopes have enabled new techniques to monitor and fix
problems more effectively and economically, especially in medicine
and industries
...

Radioisotopes have the potential to cause harm so safety precautions
need to be made
...
Therefore, steps
have to be taken to minimise harm to workers using these materials
and patients receiving them as treatment
...




THE ACIDIC ENVIRONMENT:
1
...
While we usually think of the air around us as neutral, the atmosphere
naturally contains acidic oxides of carbon, nitrogen and sulfur
...
Acids occur in many foods, drinks and even within our stomachs
4
...
Over time, the definitions of acid and base
have been refined
5
...
Indicators were identified with the observation that the
colour of some flowers depends on soil composition
Students learn to:
• classify common substances as acidic, basic or neutral
Acid- a substance able to provide hydrogen ions [H+] for chemical
reactions
Base- substances that react with acids to form salt or give rise to
hydroxide ions [OH-], soluble bases are called alkalis
Neutral- neither acidic nor basic as they do not form ions in solutions
Substance
Sodium hydroxide
(NaOH)
Ammonium
hydroxide (NH4OH)
Calcium hydroxide
(Ca(OH)2)
Water
Pure alcohol
Sugar
Hydrochloric acid
(HCl)
Sulphuric acid
(H2SO4)
Acetic acid
(CH3COOH)

Acidic/basic/neutral
Basic

Strong/weak
Strong

Basic
Basic
Neutral
Neutral
Neutral
Acidic

Strong

Acidic

Strong

Acidic

Weak

• identify that indicators such as litmus, phenolphthalein, methyl
orange and bromothymol blue can be used to determine the
acidic or basic nature of a material over a range, and that the
range is identified by change in indicator colour
Indicator
Litmus
Phenolphthalein
Methyl orange
Bromothymol blue
Methyl red

Acidic
Red
Colourless
Red
Yellow
Red

Basic
Blue
Crimson
Yellow
Blue
Yellow

Range
5
...
0
8
...
0
3
...
4
6
...
6
4
...
2

• identify and describe some everyday uses of indicators including
the testing of soil acidity/basicity
- chemists use indicators in industry to monitor the acidity/basicity of
waste as it is pumped into the rivers or seas, there are regulations
regarding the allowed acidity/basicity of wastes as they can be harmful
to the environment
- water in aquariums/fish tanks needs to be tested as fish are very
sensitive to changes in water and can survive only in water of a certain
acidity/basicity
- water in swimming pools needs to be monitored and kept close to
neutral to avoid skin and eye irritations
- soil samples need to be tested to analyse if it is appropriate for certain
plants to grow in, many plants have a very narrow pH range
...
g
...
Crush up the flowers/cabbage leaves in the stone mortar, add just
enough water to cover the pieces
2
...
Pour off the liquid, leaving the solid behind, and record the colour of
the solution
4
...
Add some of the solution to a small volume of sodium bicarbonate,
shake, and record the colour of the indicator
RESULTS:
- if you obtained different colours for the solution with the acidic
substance and the basic substance, then an acid-base indicator has been
prepared

• identify data and choose resources to gather information about
the colour changes of a range of indicators
• solve problems by applying information about the colour
changes of indicators to classify some household substances as
acidic, neutral or basic

2
...
The concentrations of these acidic oxides
have been increasing since the Industrial Revolution
Students learn to:
• identify oxides of non-metals which act as acids and describe
the conditions under which they act as acids
Acidic oxides react with bases to form salts:
acidic oxide + base à salt + water
e
...
CO2 +2NaOH à Na2CO3 + H2O
Basic oxides react with acids to form salts:
Basic oxide + acid à salt + water
e
...
MgO+ 2HCl à MgCl2 + H2O
Oxides of metals are generally basic oxides, soluble metal oxides
produce alkaline solutions:
e
...
MgO + H2O à Mg(OH)2
Most oxides of non-metals are acidic oxides
...
g
...
There are some metal oxides (e
...
zinc, lead, tin, arsenic and
aluminium) that not only react with acids to form salts, but they also
react with alkalis, these are called amphoteric oxides
...
These include CO, NO and N2O
...
g
...
Similarly three is a trend from basic oxides through a few
amphoteric oxides, to acidic oxides
...


• define Le Chatelier’s principle
Le Chatelier wrote in 188, that if a change occurs in one of the
conditions of an equilibrium system, the system would adjust, tending
to nullify the change and return to equilibrium
...
E
...
A + B à C + D, adding A drives the reaction in the
forward direction, producing more C and D, in the process, reducing
concentrations of A and B
- change in temperature – changing the temperature can alter the
equilibrium, it shifts to minimise the effect of the change
...
If P + Q à R + S is an
exothermic reaction (released), the reaction will shift to the reactant
side if the temperature is raised
- change in gas pressure – if the system involves gases, changing the
pressure will shift equilibrium
...


• describe the solubility of carbon dioxide in water under various
conditions as an equilibrium process and explain in terms of Le
Chatelier’s principle
The solubility of carbon dioxide gas in water can be fully described
using four equilibrium equations:
1
...
H2O(l) + CO2(aq)

H2CO3(aq)

3
...
HCO3-(aq)

H+(aq) + CO32-(aq)

An equilibrium shift in any of these equations leads to a change in the
concentration of the reactants and products, which influenced the
concentration in the three other reactions
...
g
...
g
...
g
...
g
...
g
...
Such
evidence comes from analysis of trapped air bubbles in Antarctic ice,
and measurement of carbon isotopes in old trees, grass seeds, and coal
...
Higher atmospheric concentrations of SOX and NOX have been
detected in industrial areas; these correspond to an increase in acidity
in lakes and rivers in these areas
2
...
34 L
...
34 / 22
...
279 moles
m(Mg) = 0
...
3
= 6
...
0mL of sulfuric acid was allowed to react with a
piece of calcium carbonate
...
Calculate the concentration of acid used
...
35 / 24
...
014 moles

c(H2SO4) = 0
...
1
= 0
...
E
...
nitrogen dioxide reacts
with water to form a mixture of nitrous and nitric acids
2NO2(g) + H2O(l) à HNO2(aq) + HNO3(aq)
Nitrous acid can be oxidised to nitric acid in the presence of the
catalyst:
2HNO2(aq) + O2(g) à 2HNO3(aq)
These rains wash out the atmosphere, but can create damage in the
ground, especially in areas where the concentrations of the gases are
high
...
The difference in mass before opening the bottle and the flat soft
drink will indicate the quantity of carbon dioxide released
...


• analyse information from secondary sources to summarise the
industrial origins of sulfur dioxide and oxides of nitrogen and
evaluate reasons for concern about their release into the
environment

3
...

A hydrogen atom, H, consists of one proton and one electron
...
A proton and a hydrogen ion are thus the same and can be
represented by a H+
...
The proton, H+, can attach to a
water molecule, H2O, forming what is called a hydrated hydrogen ion
or hydronium ion, H3O+
...
g
...
The numerical scale allows for easy
comparison of acids and bases, as bases are those with pH > 7, acids
are those with pH < 7, and neutral substances are those with pH = 7
...
A 10 mol L-1 solution would be called
concentrated
A dilute solution contains a small amount of solute in a given amount
of solution
...
01 mol L-1 solution would be called dilute
...
H+ ion concentrations can vary
widely, and the concentration of them Is very small, so the negative
logarithm of the hydrogen ion is taken:
pH = -log10[H+] / [H+] = 10-pH
A solution where [H+] = 2
...
5 x 10-5)
= 4
...
If the pH of this solution changes to 3
...
Similarly, if the pH changed from 4
...
6, then [H+] would decrease ten-fold
...
For strong
acids this is easily determined as the acid completely ionises in
solution HA à H+ + A- where HA is a strong acid
...

So [HB] > [H+]
...
g
...
05 mol L-1 solution of the weak acid HB has pH = 1
...

Calculate the degree of ionisation for this acid
[H+] = pH-1
...
016 mol L-1
0
...
05 x 100
= 32 %

• describe the difference between a strong and a weak acid in
terms of an equilibrium between the intact molecule and its
ions
A strong acid is one in which the molecules present practically all
ionise when placed in water, e
...
hydrochloric acid:
HCl + H2O à H3O+ + ClA weak acid is one where only a small proportion of the molecules
ionise when placed in water, e
...
ethanoic acid
CH3COOH + H2O à H3O+ + CH3COO-(equilibrium)

If you prepare 0
...
1 M
...
1 M solution of acetic acid will have a pH close to 3, indicating
[H+] = 10-3 = 0
...
Only about 0
...
1 = 1% of the acetic acid
molecules have ionised, producing a H+

Students:
• solve problems and perform a firsthand investigation to use pH
meters/probes and indicators to distinguish between acidic,
basic and neutral chemicals
Using a pH meter/probe is much more accurate at determining the pH
of a chemical, provided that it is washed with distilled water between
measurements
...
Using indicator solution or indicator
paper is a destructive way of testing, as the indicator will contaminate
the solution
...
g
...
1 mol L-1
C1V1 = C2V2
2 x 50 = 0
...
1 = 1000 mL (needs to be diluted to 1000 mL)

• gather and process information from secondary sources to
write ionic equations to represent the ionisation of acids
• use available evidence to model the molecular nature of acids
and simulate the ionisation of strong and weak acids
• gather and process information from secondary sources to
explain the use of acids as food additives
Acids are added to foods to improve taste and to preserve them
...
Common acids used include acetic acid, citric
acid, tartaric acid, and phosphoric acid

• identify data, gather and process information from secondary
sources to identify examples of naturally occurring acids and
bases and their chemical composition

- acetic acid, CH3COOH: vinegar
- butyric acid, CH3CH2CH2COOH: butter
- stearic acid, CH3(CH2)16COOH: beef suet
- oxalic acid, HOOCCOOH: foods such as rhubarb
- salicylic acid: medicines such as aspirin and oil of wintergreen
- lactic acid, CH3CHOHCOOH: sour milk, cheese, wine, sauerkraut
- citric acid: found in the juices of fruits
- tartaric acid: prepared from grape juice ferments

• process information from secondary sources to calculate pH of
strong acids given appropriate hydrogen ion concentrations
In a strong acid solution, each acid molecule is assumed to fully ionise
...

e
...
HCl
HCl à H+ + Cl[H+] = concentration of HCl
e
...
H2SO4
H2SO4 à 2H+ + SO42[H+] = 2 x concentration of H2SO4
pH = -log10[H+]

4
...
Over time, the
definitions of acid and base have been refined
Students learn to:
• outline the historical development of ideas about acids
including those of:
– Lavoisier: through experimentation, was lead to believe that all
acids contain oxygen, and it was this oxygen that gave rise to their
acidity
...
He
proposed that bases ionise to produce hydroxide ions in solution,
and he realised that the strength of the acid depended on the degree
of ionisation and was able to explain that neutralisation was a
reaction between the hydrogen ion of an acid and the hydroxide ion
of a base: H+(aq) + OH-(aq) à H2O(l)

• outline the Brönsted-Lowry theory of acids and bases
A theory, based on proton transfer, was outlined by Bronsted and
Lowry
...

If in a solvent, a substance HA has a greater tendency to give up
protons than the solvent, then HA is an acid
...
g
...

If another substance, B, has a greater tendency to accept protons than
the solvent, then it is a base in that solvent
...
g
...


• describe the relationship between an acid and its conjugate
base and a base and its conjugate acid
When an acid donates a proton, it forms its conjugate base:
HCl

+ H2 O
acid

Cl+ H3 O+
conjugate base

When a base accepts a proton, it forms its conjugate acid:
HCl + H2O
Cl- + H3O+
base
conjugate acid
- a strong acid has a weak conjugate base
- a weak acid has a strong conjugate base
- a strong base has a weak conjugate acid
- a weak base has a strong conjugate acid

• identify a range of salts which form acidic, basic or neutral
solutions and explain their acidic, neutral or basic nature
A salt is formed when an acid is neutralised by a base
...

- A salt formed from a weak acid and a strong base will produce a
solution, pH > 7 in water
- A salt formed from a strong acid and a weak base will produce a
solution,
pH < 7 in water
- a salt formed from a strong acid and a strong base will produce a
neutral, or approximately neutral solution, pH = 7 in water
- a salt formed from a weak acid and a weak base will produce a
neutral, or approximately neutral solution, pH = 7 water

• identify conjugate acid/base pairs
Whenever an acid and a base react, they form their conjugates:
HCl
acid1

+

H2 O
Clbase2
conjugate base1

+
H3 O+
conjugate acid2

- hydrochloric acid and chloride ion are a conjugate acid-base pair
- water and hydronium ion are another conjugate acid-base pair

• identify amphiprotic substances and construct equations to
describe their behaviour in acidic and basic solutions
Some ions have the ability to either donate protons or accept protons,
e
...
with water:
Water donates proton: NH3 + H2O à NH4+ +OHWater accepts proton: HSO4- + H2O à SO42- + H3O+
Amphiprotic substances are molecules or ions that can behave as both
Bronsted-Lowry acids and bases, they can either donate or accept a
proton
...


• identify neutralisation as a proton transfer reaction which is
exothermic
The neutralisation reaction is: acid +base à salt + water:
e
...
HCl + NaOH à NaCl + H2O
H+ + Cl- + Na+ OH- à Na+ + Cl- + H2O
The net ionic equation for the reaction is:
H3O+ + OH- à H2O
The net ionic equation shows that neutralisation is a proton transfer
reaction, a proton from the acid transfers to the hydroxide ion of the
base
...
The enthalpy
change for neutralisation reactions is around 57 kJ mol-1
H3O+(aq) + OH-(aq) à H2O(l)

∆H = -57 kJ mol-1

• describe the correct technique for conducting titrations and
preparation of standard solutions
Steps in Titrating:
- rinse burette with a small amount of solution of known concentration
- fill burette and run out the excess so the solution is level with the
zero mark
- use pipette to measure a given volume of solution of unknown
concentration into a flask and place under the burette
- add two or three drops of indicator to solution
- slowly run titrant into the flask, swirling continuously to mix, near
the equivalence point, add the titrant slower
- repeat titration at east 3 times

Determining End Point of Titration:
- strong acid/strong base titrations have end points around pH = 7, an
appropriate indicator would be bromothymol blue as it changes from
yellow to blue between 6
...
6
- weak acid/ strong base titrations have end points around pH = 9, an
appropriate indicator would be phenolphthalein as it changes from
colourless to pink between 8
...
0
- strong acid/weak base titrations have an end point around pH = 4, an
appropriate indicator would be methyl orange as it changes from red to
yellow between 3
...
4

• qualitatively describe the effect of buffers with reference to a
specific example in a natural system
A buffer is solution that resists any great change in pH when small
quantities of acid or base are added to it
...

CO2(aq) + H2O(l) à H2CO3(aq)
H2CO3(aq) à HCO3- + H+(aq)
As CO2 builds up in our plasma from respiration, more H2CO3 is
formed
...
The kidney kicks in and releases
HCO3- into the bloodstream, driving the reaction in the opposite
direction thereby consuming H+(aq) ions
...


• perform a first-hand investigation and solve problems using
titrations and including the preparation of standard solutions,
and use available evidence to quantitatively and qualitatively
describe the reaction between selected acids and bases
AIM: to titrate a sample of white vinegar, to determine its
concentration of acetic acid
EQUIPMENT:
- 3 flasks
- pipette
- burette
- distilled water
- 0
...
Transfer 25 mL of vinegar to each of the three conical flasks,
labelling them A, B and C
2
...
Fill the burette will standardised 0
...
Titrate flask until the first permanent pink colour is reached, record
results and repeat with flasks B and C
RESULTS:
A
Initial reading (mL) 0
...
2
17
...
1
24
...
8

CALCULATIONS:
Average volume = 0
...
0172 x 0
...
00172 mol
CH3COOH + NaOH à CH3COONa + H2O
[acetic acid] = 0
...
025
= 0
...
01 = 0
...
1
= 0
...

They can be far more accurate, time-saving and efficient
...
Water can absorb a relatively large
amount of heat
- spills of acids or bases on bench tops or floors can be safely
neutralised using weak bases, or weak acids
...
Esterification is a naturally occurring process which can be
performed in the laboratory
Students learn to:
• describe the differences between the alkanol and alkanoic acid
functional groups in carbon compounds
The alkanols form a homologous series of carbon compounds
containing the hydroxyl group, OH-
...
The
general formula fro alkanols is R-OH where R stands fro the carbon
chain CnH2n + 1
...
It is the functional group that
gives alkanoic acids their distinctive physical and chemical properties
...

Features of alkanoic acids include:
- they are polar compounds due to the presence of the carboxyl group
- strong hydrogen bonds form between nearby molecules
- they are water soluble due to this hydrogen bonding, but this
solubility decreases with increasing carbon chain length
- they have higher melting and boiling points than corresponding
alkanes, alkenes and alkanols
- they are weak acids as they partly dissociate in water:
RCOOH(aq) à RCOO-(aq) + H+(aq)
-they react with alkanols to form esters
- salts of long chain alkanoic acids are soaps

• identify the IUPAC nomenclature for describing the esters
produced by reactions of straight-chained alkanoic acids from
C1 to C8 and straight-chained primary alkanols from C1 to C8

Alkanol

Methanol
Ethanol
Propanol
Butanol
Pentanol
Hexanol
Heptanol
Octanol

Methanoic
acid
Methyl
methanoate
Ethyl
methanoate
Propyl
methanoate
Butyl
methanoate
Pentyl
metanoate
Hexyl
methanoate
Heptyl
methanoate
Octyl
methanoate

Ethanoic
acid
Methyl
ethanoate
Ethyl
ethanoate
Propyl
ethanoate
Butyl
ethanoate
Pentyl
ethanoate
Hexyl
ethanoate
Heptyl
ethanoate
Octyl
ethanoate

Propanoic
acid
Methyl
propanoate
Ethyl
propanoate
Propyl
propanoate
Butyl
propanoate
Pentyl
propanoate
Hexyl
propanoate
Heptyl
propanoate
Octyl
propanoate

Alkanoic acids
Butanoic
Pentanoic
acid
acid
Methyl
Methyl
butanoate pentanoate
Ethyl
Ethyl
butanoate pentanoate
Propyl
Propyl
butanoate pentanoate
Butyl
Butyl
butanoate pentanoate
Pentyl
Pentyl
butanoate pentanoate
Hexyl
Hexyl
butanoate pentanoate
Heptyl
Heptyl
butanoate pentanoate
Octyl
Octyl
butanoate pentanoate

Hexanoic
acid
Methyl
hexanoate
Ethyl
hexanoate
Propyl
hexanoate
Butyl
hexanoate
Pentyl
hexanoate
Hexyl
hexanoate
Heptyl
hexanoate
Octyl
hexanoate

• explain the difference in melting point and boiling point
caused by straight-chained alkanoic acid and straight-chained
primary alkanol structures
Alkanols contain C-O and O-H bonds, which are polar
...
There are
strong intermolecular forces in alkanols, therefore none are gases at
room temperature
Alkanoic acids contain another polar group C=o, as well, so their
intermolecular forces are even greater than that of their corresponding
alkanols
...


• identify esterification as the reaction between an acid and an
alkanol and describe, using equations, examples of
esterification
The reaction between an alkanoic acid and an alkanol is called
esterification
Alkanoic acid + alkanol à ester + water

Heptanoic
acid
Methyl
heptanoate
Ethyl
heptanoate
Propyl
heptanoate
Butyl
heptanoate
Pentyl
heptanoate
Hexyl
heptanoate
Heptyl
heptanoate
Octyl
heptanoate

Octanoic
Acid
Methyl
octanoate
Ethyl
octanoate
Propyl
octanoate
Butyl
octanoate
Pentyl
octanoate
Hexyl
octanoate
Heptyl
octanoate
Octyl
octanoate

e
...
HCOOH + CH3CH2OH à HCOOCH2CH3 + H2O
methanoic acid acid + ethanol à ethyl methanoate + water
The underlined atoms join together to form water, so esterification is
an example of a condensation reaction
...
The addition of a concentrated mineral acid, such as
sulfuric acid, serves as a catalyst as it speeds up the reaction
...

A strong acid like sulfuric acid can donate a proton to the unshared
electron pairs of either the acid or the alkanol, this makes either of
them more reactive
...


• explain the need for refluxing during esterification

Esterification is used to prepare esters in high yields by carefully
controlling the reaction conditions
...
g
...

Heating is necessary to proceed the reaction to a reasonable speed, as
esterification can take days
...


By refluxing, volatile components cool in an upright condenser and
flow back into the reacting vessel, where they can resume their role in
the reaction
...

Boiling chips are added to the reaction mixture to provide nucleation
centres and promote even boiling
...
To ensure a more even heating, a
water bath is used in place of aiming a Bunsen burner directly under
the flask
...
They may occur naturally or be produced
artificially
...
Some uses of esters include:
- food (e
...
margarine, fats, and as fragrances and flavours)
- soaps
- solvents (e
...
dissolving both polar and non-polar organic
compounds)
- medical uses (e
...
nitro glycerine used to dilute blood vessels)
- other uses such as emulsifying agents and emollients in cosmetics, in
commercial oil and linoleum

Students:
• identify data, plan, select equipment and perform a first-hand
investigation to prepare an ester using reflux
AIM: to prepare an ester using reflux
EQUIPMENT:
- water bath
- boiling chips
- condensing chamber
- volumetric flask
- pentanol
- ethanoic acid
- sulphuric acid
SAFETY PRECAUTIONS:
- wear gloves to avoid acid touching skin
- use boiling chips to prevent bumping when boiling
METHOD:
1
...
Measure out 20mL of ethanoic acid into the same flask
3
...
Heat under reflux for one hour, add boiling chips
5
...
It is
easier to mass produce inexpensive synthetic esters for use as flavours
and perfumes in processed foods and cosmetics than to use naturally
occurring ones
...
Much of the work of chemists involves monitoring the reactants and
products of reactions and managing reaction conditions
2
...
Manufactured products, including food, drugs and household chemicals,
are analysed to determine or ensure their chemical composition
4
...
Chemists monitor these changes so that further damage
can be limited
5
...
Chemical monitoring and
management assists in providing safe water for human use and to protect the
habitats of other organisms

1
...
The person can direct the
project and assign various tasks to chemists in their team according to
their expertise each individual brings to the group
...
These chemists may be part of a team, or if
their expertise is needed for only part of the time, may be shared across
a number of teams and projects
Chemists may work in collaboration with other scientists, or people
outside the science field to achieve their objective
...

• If you need a high temperature flame, the air hole is fully open so
that oxygen reaches the gas for complete combustion:
e
...
methane:
CH4(g) + 2O2(g) à CO2(g) + 2H2O(g)

e
...
propane
C3H8(g) + 5O2(g) à 3CO2(g) + 4H2O(g)
• If the air hole is partly open, incomplete combustion occurs,
producing some carbon monoxide:
e
...
methane:
CH4(g) + 3/2O2(g) à CO(g) + 2H2O(g)
e
...
propane:
C3H8(g) + 7/2O2(g) à 3CO(g) + 4H2O(g)
• If the air hole is not open at all, carbon is produced
...
g
...
g
...
The more complete the combustion,
the greater the amount of energy released
...


Students:
• gather, process and present information from secondary sources
about the work of practising scientists identifying:
– the variety of chemical occupations
e
...
research assistants (pharmaceuticals, microbial chemistry,
physiology, healthcare etc
...
He works in medical
research, specifically human physiology
...


2
...
When nitrogen and hydrogen are initially added to the
reaction vessel, the reaction is slow; equilibrium is reached when the
rate of the forward reaction is the same as the rate of the reverse
reaction
...
This gives the reaction a negative ∆H
value, meaning it is exothermic, shown in the equation:
N2(g) + 3H2(g) à 2NH3(g)

∆H = -92 kJ

• explain why the rate of reaction is increased by higher
temperatures
As the temperature is increased, the particles move and vibrate faster
...
You would expect the increased rate of collisions to increase
the rate of formation of ammonia
...


• explain why the yield of product in the Haber process is
reduced at higher temperatures using Le Chatelier’s principle
The forward reaction in which ammonia is formed is exothermic,
meaning heat is a product:

Le Chateliers principle states that if a system in equilibrium is
disturbed, the system will adjust itself to minimise the disturbance
...
However increasing the temperature shifts
equilibrium to the left, forming more nitrogen and hydrogen than
ammonia
...

Increasing the pressure in the reaction, increases the yield of ammonia,
as equilibrium is shifted to the right (the side with the least amount of
moles of gas)
...
A compromise of pressure must be selected to maintain
optimal yield while keeping the cost down and keeping the process as
safe as possible
...
A finely ground iron catalyst
(with a large surface area) is used in the Haber process
...
Lowering the
activation energy with a catalyst, allows a more rapid reaction at lower
temperatures
...
According to Le Chatelier’s principle, increasing the
pressure favours the production of ammonia, because the two moles of
gaseous ammonia occupy a smaller volume than the four moles of
reactants
...

High pressure also increases the reaction rate because the gas
molecules are closer and at higher concentrations

• explain why monitoring of the reaction vessel used in the
Haber process is crucial and discuss the monitoring required
The Haber process is a continuous, around-the-clock event
...

•

•
•

•

•

•
•

The feedstock (nitrogen and ammonia), must be pure and free
from contaminant, as these can interfere with the yield and can
damage the catalyst
...
g
...
Large quantities of food were
needed to feed burgeoning populations, especially in America and
Europe
...
Ammonia was also needed to
produce explosives for the war effort
...
Peruvian guano and
sodium nitrate from Chile had become exhausted by 1900
...

As Germany needed to meet increasing demands of fertilisers and
explosives, Haber developed an industrial process to develop ammonia
from atmospheric nitrogen
...

Without the development of the Haber process, Germany would not
have been able to maintain their war effort, as they would’ve run out
of food, and explosives
...


3
...
Special, hollow cathode lamps emit light
with these frequencies and this is absorbed by the metal being
examined
...
This is compared to the absorption
of known concentrations of standard solutions
...
They occur somewhere in the range of 1 to 100 ppm in living
organisms and being able to detect them in such low concentrations

has allowed scientists to work out how they assist in the healthy
functioning of the organism
...

e
...
Functions of some metallic trace elements
Metal
Copper

Function
• haemoglobin formation
• enzyme action
Zinc
• enzyme action
• metabolism of amino acids
• insulin synthesis
Selenium
• enzyme action
Manganese • enzyme action
• blood clotting
• carbohydrate and fat metabolism
Cobalt
• red blood cell formation
AAS is also used to monitor concentrations of heavy metals that can
be toxic to animals, humans and plants
...
Zinc, lead, copper and cadmium
have all been reported in elevated concentrations than at the time of
the First Fleet
...


• deduce the ions present in a sample from the results of tests
Test for anions:
Anion
Carbonate
(CO32-)

Sulfate (SO42-)

Test
• add dilute HCl
CO32- + 2H+ à CO2(g)
H2O(l)
CO2 + Ca(OH)2 à CaCO3 +
H2 O
• add barium ions
SO42- + Ba2+ à BaSO4(s)

Chloride (Cl-)

• add silver nitrate

Phosphate
(PO43-)

• add silver nitrate

Nitrate (NO3-)

• add ammonia, then
Ba(NO3)2
• add FeSO4 then
concentrated H2SO4

Positive Result
• carbon dioxide
formed
• turns limewater
milky
• white precipitate of
barium sulfate
(insoluble in dilute
HCl)
• white precipitate of
silver chloride
Ag+ + Cl- à AgCl(s)
• yellow cloudiness
• white precipitate
• brown ring at the
junction of two
solutions

Test for Cations:
Cation
Barium (Ba2+)

Calcium (Ca2+)

Lead (Pb2+)
Copper (Cu+ or
Cu2+)
2+

Iron (Fe )/Iron
(Fe3+) [oxidises to
Fe3+ on standing]

Test
• flame test
• add sulfate ions
SO42- + Ba2+ à
BaSO4(s)
• flame test
• add carbonate ions
Ca2+ + CO32- à
CaCO3(s)
• add iodide ions
Pb2+ + 2I- à PbI2(s)
• flame test
•
•

add hydroxide ions
add hydroxide ions

Positive Result
• lime-green flame
• white precipitate of
barium sulfate
• orange-red flame
• white precipitate of
calcium carbonate
• yellow precipitate of
lead iodide
• blue-green flame
• deep blue precipitate
• white precipitate of
iron(II)hydroxide,
oxidises to red-brown
iron(III)hydroxide

Students:
• perform first-hand investigations to carry out a range of tests,
including flame tests, to identify the following ions:
– phosphate
– sulfate
– carbonate
– chloride
– barium
– calcium
– lead
– copper
– iron

• gather, process and present information to describe and explain
evidence for the need to monitor levels of one of the above ions
in substances used in society
Water – Water is analysed for the presence of trace elements
...
A very minute amount of metallic and non-metallic elements is
acceptable for water to be potable
...
Much of his fertiliser
finds its way into aquatic ecosystems where the increased growth of
algae caused by artificial eutrophication in natural systems can be
detrimental
...
Some 95% of air-borne lead was released by petrol
combustion
...
In humans, lead poisoning can produce nausea and lack of
appetite, as well as destructive behaviour patterns and brain damage
...

Monitoring lead concentrations in the human environment and the
effects of lead on biological systems has prompted governments to ban
this as an additive to petrol and paints
...
Dissolve an accurate measure of fertiliser (1g) in some distilled water
and make up to 500 mL in a volumetric flask
2
...
Acidify
this with a few millimetres of dilute hydrochloric acid and warm
3
...
When no more precipitate forms, discontinue adding barium
chloride
4
...
Filter the precipitate through the filter paper, washing the precipitate
with several aliquots of hot, distilled water
6
...
Calculate the mass of barium sulfate
RESULTS:
• 100 mL of fertiliser yielded 0
...
410 / 233
...
001757 moles
n(SO42-) = 0
...
001757 x 96
...
169 g
• in 500 mL flask
= 5 x 0
...
845 g
% (SO42-) = 0
...
12 x (100)
= 75
...
Precipitating from a hot solution will allow you to
obtain a more accurate measure of the barium sulfate precipitate
...
Wash the precipitate several times with warm
distilled water to remove soluble particles, then thoroughly dry it in a
desiccator
Validity – the assumption on which validity relies is that all the barium
sulfate, and only barium sulfate particles will precipitate
...
This is why you repeat experiments and obtain an
average value from closely agreeing values
...

All measurements need to be accurately done, and an electronic balance
will give you an accurate mass
...
The reason for changing the soluble sulfate in
fertiliser to BaSO4 is that this substance is highly insoluble, meaning
very little of it will remain in solution when you filter the precipitate
...
Washing the precipitate with distilled
water removes any soluble particles that may have been inadvertently
attached themselves to it
...
The greatest improvements in air quality are brought about
by legislative control
...
Human activity has caused changes in the composition and
the structure of the atmosphere
...
Ozone can absorb much of the harmful UV-C
and UV-B radiation, preventing it from reaching the Earth’s surface

• describe the formation of a coordinate covalent bond
A coordinate covalent bond forms when one atom in a species (a
molecule or ion contained non-metallic atoms) provides both
electrons in the covalent bond
...
A coordinate
covalent bond is simply a covalent bond where both of the shared
electrons have been donated by the same atoms
...


• demonstrate the formation of coordinate covalent bonds using
Lewis electron dot structures
In O2 there is a double bond between the oxygen atoms: O=O,
therefore there are two pairs of shared electrons in O2
...
When
O2 forms, two pairs of electrons are shared between these O atoms,
leaving two unshared pairs of electrons on each O atom
...
To form the stable
octet of electrons around each O atom a coordinate covalent bond
forms between a O atom and one of the unshared pairs of electrons
on the O2 molecule
...
3 g/L
Water solubility • sparingly soluble, about 4
...
0 g/L
more soluble than
O2
readily dissolves in
turpentine,
cinnamon oil and
many other organic
liquids containing
one or more
ethylene linkages
poisonous and
harmful to living
things
highly reactive with
chemicals and
living tissue
easily decomposed
to O2
effect of UV light
on O2
electric discharge
on O2
germicidal action
(sterilising drinking
water, surgical
instruments)
bleaching agent in
paper and textile
manufacture
powerful oxidising
agent

• compare the properties of the gaseous forms of oxygen and
the oxygen free radical
The oxygen atom in its ground state has 3 pairs of electrons in its
valence shell
...
e
...
The energy absorbed in the splitting
and the unpaired electrons make the free radical very reactive
...


• identify the origins of chlorofluorocarbons (CFCs) and halons
in the atmosphere
CFCs are compounds containing only chlorine, fluorine and carbon
...

CFCs are odourless, non-toxic, non-flammable, inert substance that
were developed in the 1930s as replacements for ammonia in
refrigerants
...
They are dense, nonflammable liquids that found use in fire extinguishers, especially
those used where there is electrical equipment
...
It was found that CFCs were so inert that they did not
react in the troposphere
...

Halon use has been drastically reduced because it was found that
bromine atoms are even more effective than chlorine atoms in the
chain reactions that lead to the depletion of ozone
...
They consist of the same types and numbers of
atoms but are arranged in different ways
...
g
...
CFCs eventually make their way to
the stratosphere where the UV energy results in them photo
dissociating to release reactive chlorine radicals

CCl3F à Cl• + •CCl2F
CCl2F2 à Cl• + •CCLF2
The free chlorine radical can now catalyse the reaction of ozone to
oxygen
Cl• + O3 à ClO• + O2
ClO• + O• à Cl• + O2
Overall : O + O3 à 2O2
The free chlorine radical is free to continue this process many tens of
thousands of times before it meets some other species that will
remove it from the loop
...

The depletion of the protective ozone layer by CFCs was first noticed
in the 1970s
...
Measurements over Antarctica have shown a 5090% decrease in ozone
...
Over the years, more counties have signed the protocol
...
Developed nations have
now effectively eliminated the production of ozone-depleting
substances
...
The decline
approximated 30% by 1985
...

Measurements of ozone levels in the atmosphere can be obtained
using UV spectrophotometers
...
Measurements
were taken by British scientists in the Antarctic using UV
spectrophotometers directed vertically up
...

Helium balloons, satellites and aircrafts were used to obtain
measurements
...
The chlorine atom radical then rapidly reacts with an
ozone molecule to produce the chlorine oxide molecule, ClO
...

CF3Cl à CF3 + Cl
Cl + O3 à ClO + O2
ClO + O à Cl + O2
Ozone depletion is more frequent in winter and spring due to more ice
particles, which provide a surface to act as a catalyst
...

Despite our efforts to stop using CFCs, it is taking a very long time for
the destruction of ozone to decline as the chlorine acts as a catalyst in
this cycle for a very long time
...
For example, HCFCs and HFCs
...
In the troposphere they are
oxidised to form CO2, H2O and HX (X=halide), so very little of them
reaches the stratosphere to interfere with ozone
...
They react more readily than HCFCs with OH in the
troposphere, and because they do not contain chlorine, they re not
expected to produce chlorine radicals in the stratosphere
...
Human activity also impacts on waterways
...
5 and 8
...
2H2O)or over limestone
chalk (CaCO3), while CaCO3 is practically insoluble, CO2 dissolved in
water increases its solubility
- rivers contain differing quantities and kinds of dissolved matter
according to the nature of the landmass over which it flows
...
g
...
Rivers are also frequently contaminated with
sewage an factory wastes, while tidal rivers are twice a day salty at
some considerable distance from their mouths, owing to the influx of
the tide
...
Acting as the worlds scavenger, sea
water has amassed a variety of solutes

• describe and assess the effectiveness of methods used to purify
and sanitise mass water supplies
1
...
Screening – large insoluble matter is screened out using sieves
3
...
Filtration – sand filters remove fine, suspended solids and some
microorganisms, while they are effective, they require large land areas
to fulfil the water demands of modern cities
...
Adsorption – activated carbon and ion exchange resins can be used
as adsorbants to remove soluble contaminants from the water
...
Ion exchange resins work
by exchanging ions in the water with those on the resin
6
...
Water stabilisation – pH should remain close to 7,many waters are
stabilised by adding lime and sometimes carbon dioxide
8
...

Chloramines form when chlorine and ammonia are added together,
they are not as effective as chlorine at killing micro-organisms, but
they maintain their disinfecting ability longer and react less with
organic matter
...

Ozone is the most powerful disinfectant
...
As it is so reactive, its life in water is short lived and is
usually used with longer lasting chlorine
...
It is effective and has no
lasting effect, however, impurities in the water reduce the effectiveness
of UV irradiation
...
Membrane filtration technique can
be simple and reliable , though there are high energy costs in pumping
the water through the membrane and organic matter can cause the
membrane to be fouled
...

Microfiltration (pore size: ~0
...
It cannot remove
dissolved organic matter
Ultrafiltration (pore size: ~0
...
001 microns) – this requires even higher
pressures to force water through the membrane, thereby increasing
operating and energy costs
...
Techniques to identify the presence of heavy
metals include precipitation and flame test, but to quantitatively
determine heavy metals tests used include volumetric and gravimetric
analysis and AAS
...
As
they die, this causes oxygen depletion during the decay process, due to
bacterial action
...

Algal blooms also have the potential to produce poisons detrimental to
humans and animals
...
Tests to determine the extent of eutrophication include
the measurement of dissolved oxygen and nutrients, such as nitrates
and phosphates
...
g
...
g
...
The chemical composition of the ocean infers its potential role as an
electrolyte
2
...
Electrolytic cells involve oxidation-reduction reactions
4
...
When a ship sinks, the rate of decay and corrosion may be dependent on
the final depth of the wreck
6
...
Salvage, conservation and restoration of objects from wrecks requires
careful planning and understanding of the behaviour of chemicals

1
...
Over billions of years the quantity of salts becomes substantial
...
Ions added to the sea this way include
iron, sodium, potassium, calcium, sulfates, hydrogen carbonates and
silicates

– hydrothermal vents in mid-ocean ridges
Mid-oceanic ridges are the sites of geothermic activity
...
As the rock cools,
it cracks, allowing sea water to sink in and be heated to around 350º400ºC, and is also under great pressure
...
These vents are sources of copper, zinc and iron which from
insoluble deposits on the ocean floor
...
The species that loses the electrons is the reductant,
and the species that gains the electrons is the oxidant
...

The net equation is:
Cu(s) + 2Ag+(aq) à Cu2+(aq) + 2Ag(s)
Copper is the reductant, and loses two electrons, therefore it is oxidised:
Cu(s) à Cu2+ + 2eThe electrons are picked up by the silver ions
...
In this reaction,
nitrate is a spectator ion, meaning it is an ion present in the solution that
does not take any part in the reaction
...

E
...
in the reaction: Cu(s) + 2Ag+(aq) à Cu2+(aq) + 2Ag(s)
Silver ions in solution migrate randomly towards the surface of the
copper
...
The silver ions now become
insoluble silver atoms and deposit on the copper
...

The reaction is quite rapid
...


• describe the work of Galvani, Volta, Davy and Faraday in
increasing understanding of electron transfer reactions
Luigi Galvani: He placed the ends of two dissimilar metals in contact
with the muscle of freshly killed frogs
...
He was unaware that the two dissimilar metals in contact
could generate an electric current
...
He developed the
‘Voltaic pile’, which was a pile of alternating discs of two different
metals
...
The voltaic pile
formed a primitive battery
...

Sir Humphrey Davy: Davy improved on the voltaic pile and performed
experiments with it
...

He further realised that these reactions were decomposition reactions, by
using electrolysis to decompose water into hydrogen and oxygen
...
He invented a process to
desalinate water, and was able to show how ships could be protected
from corrosion by attaching zinc plates to them
...
He was
able to propose two laws of electrolysis:
1
...
The amount of substance produced or dissolved at an electrode by
passing the same amount of electricity are inversely proportional to the
charges on their ions
One of Faradays major contributions was quantitative electrochemistry:
measurements could be made to predict the amount of substance
produced or dissolved and link that to the quantity of electricity
...
Sometimes the interpretations are incorrect and
other scientists, will make corrections in light of experimental evidence
...

This first battery caused considerable excitement throughout Europe and
soon the voltaic pile made its way into all scientific laboratories
...

Davy then used this pile, discovering the true nature of alkalis
...
Until then alkalis had been regarded as elements
...
Their large-scale application became possible only when
electrical engineering had progressed sufficiently
...


2
...
In moist air most metals form a surface layer
of oxide, depending on the nature of the oxide it may slow down or
prevent corrosion
...

Corrosion of passivating metals:
Passivating metals are reactive metals that spontaneously form a
strongly adhering coating that protects the metal from sny further
corrosion
...
For example when aluminium reacts with oxygen, it forms
aluminium oxide, which adhered to the surface as a non-porous, inert
layer, preventing aluminium from further oxidation
...
Steel has the advantages of
being of good mechanical strength, being relatively hard, and it can be
rolled into sheets and pressed into desired shapes
...

Bronze is also used in propellers in ships as they are resistant to
corrosion in salt water, unlike steel propellers
...


• identify the composition of steel and explain how the percentage
composition of steel can determine its properties
The hardness and tensile strength of steel increases as the carbon
content increases
...


Carbon Steel
Type
Low carbon
steel

Composition
0
...
25 % C

Medium
carbon steel

0
...
60 % C

High carbon
steel

0
...
2 % C

Cast iron

2
...
8 % C
1
...


Alloy Steel
Elements
Chromium,
chromium/vanadium

Nickel

Cobalt
Titanium
Tungsten

Silicon

Nickel/chromium

Features
• hardness
• strength and
elasticity
• increased resistance
to wear and
corrosion
• increased strength
• has tensile properties
of high carbon steel
without brittleness
• easily magnetised
using an electric
current
• increased hardness
and tensile strength
• high melting
temperature
• tough
• easily magnetised
and demagnetised
• resilient
• shock resilient
qualities
• corrosion resistant
(hence stainless
steel)

Examples
• aeroplanes
• automobiles
• ball bearings
• safes
• heavy vehicle gears
• crankshafts
• electromagnets
• high speed tools
• permanent magnets
• cutting, grinding
and drilling tools
• drill bits
• electromagnets
• springs
• armour plating
• surgical
instruments

• describe the conditions under which rusting of iron occurs and
explain the process of rusting
Iron is oxidised:
Fe(s) à Fe2+(aq) + 2eOxygen dissolved in water is reduced:
O2 (aq) + 2H2O (l) + 4e- à 4OH-(aq)
The iron(II) hydroxide precipitates:
Fe2+(aq) + 2OH-(aq) à Fe(OH)2 (s)
The iron(II) hydroxide oxidises to hydrated iron(III) oxide:
Fe(OH)2 (s) + O2 (aq) à 2Fe2O3
...
H2O(s)

Conditions promoting rusting:
- acidic conditions promote the dissolution of iron
...
The
reduction potential is more positive than for the corresponding equation
in neutral or alkaline solutions
- electrolytes in water assist in the process by increasing the
conductivity of the solution
...
An
electrochemical cell is set up where iron becomes the anode and is
oxidised, while the other metal becomes the cathode, where oxygen is
reduced in the film of water
- stresses in the iron lattice waken it so that the iron atoms are not
strongly held
...
Stresses occur where
nails or wire are bent or at tips and sharp edges
- contact with less active metals, provides surfaces where oxygen
reduction can occur
...
5 mL HCl (for acidified water)
- 0
...
Obtain 6 samples of about the same size and shape of iron, steel and
stainless steels
2
...
Stopper each of the 18 test tubes and observe the results everyday for
two weeks
RESULTS:
- stainless steel should show the least rusting; the other samples will
depend on the carbon content
- rusting occurs most readily when both water and oxygen are present, it
also occurs more rapidly in acidified water than alkaline water
CONCLUSION:
- iron corrodes at a much faster rate than steels, with stainless steel
being the most resistant to corrosion

• use available evidence to analyse and explain the conditions
under which rusting occurs
• gather and process information from secondary sources to
compare the composition, properties and uses of a range of steels

3
...
23 V
The reaction at the cathode is:
2H2O + 2e- à H2 + 2OHEø = -0
...
06 V
The negative sign indicates that the reaction is not spontaneous in this
direction
...

The Electrolysis of Aqueous Copper Sulfate:
In an aqueous solution of copper sulfate the positive ion present is Cu2+
and the negative ion is SO4 2-
...

At the cathode there are two possible reactions:
Cu2+ + 2e- à Cu
Eø = 0
...
83 V
The equation with the lower numerical value for Eø is preferred so the
copper ion discharges
...
01 V
+
2H2O à O2 + 4H + 4e
Eø = -1
...

The overall (net) equation is:
2Cu2+ (aq) + 2H2O (l) à 2Cu (s) + O2 (g) + 4H+ (aq)

Eø = -0
...

The higher the voltage the greater the current
...
The cell potentials given on standard potential tables are
measured using 1 molL-1 concentration electrolyte solution
...

Increased concentrations of ions, increase the current and consequently
the rate of electrolysis
...


– nature of electrolyte
Molten electrolytes with inert electrodes, can yield only one product
for each electrode
...

In aqueous solution there is also the possibility that water will be one
of the reactants at one or both of the electrodes
...
10 V
2Br (aq) à Br2 (l) + 2e
Eø = -1
...
23 V
The equation with the lower numerical value for Eø is preferred and so
the bromide ion discharges as liquid bromide
...
36 V
2H2O (l) + 2e à H2 (g) + 2OH (aq)
Eø = -0
...
If the electrodes are not inert they may partake in the
reaction
...

Increased surface area of the electrode used increases the current and
rate of electrolysis
...


Students:
• plan and perform a first-hand investigation and gather firsthand data to identify the factors that affect the rate of an
electrolysis reaction
EXPERIMENT: Identifying factors affecting the rate of electrolysis
AIM: to investigate the factors that affect the rate if an electrolysis
reaction using the electrolysis of copper sulfate solution with copper
electrodes
EQUIPMENT:
For each group:
- 250 mL beaker
- 2 clock glasses
- fine sandpaper
- electronic balance
- DC power source
- 2 electrical leads with clips
For part A:
-2 copper strips for electrodes; 2 cm wide and 6 cm long
- 100 mL 1
...
0 molL-1 copper sulfate solution
For part C:
-2 copper strips for electrodes; 2 cm wide and 6 cm long
- 100 mL 1
...
10 molL-1 copper sulfate solution
METHOD:
1
...
Place electrodes in beaker with appropriate amount of copper sulfate
solution, ensuring both electrodes are immersed to the same depth
3
...
Electrolyse for 30 minutes, remove electrodes and allow to dry
...
0 mol/L concentration electrolyte

Part B: Electrolyse at 2V using 5 cm wide strips, same distance apart as
A and 1
...
0 mol/L concentration electrolyte
Part
A1
A2
A3
B
C
D

Electrodes Separation
(cm)
(cm)
2
2
2
5
2
2

2
2
2
2
5
2

Concentration
(mol/L)
1
...
0
1
...
0
1
...
10

Voltage
Mass of Anode (g)
Initial Final Change
(V)
2
4
6
2
2
2

5
...
91
5
...
7
5
...
88

4
...
43
4
...
76
4
...
78

-0
...
48
-0
...
94
-0
...
1

Part D: Electrolyse at 2 V using 2 cm wide strips, same distance apart
as A but 0
...
17
5
...
19
16
...
62
5
...
79
5
...
63
18
...
92
5
...
62
+0
...
44
+2
...
3
+0
...
Iron and steel corrode quickly in a marine environment and
must be protected
Students learn to:
• identify the ways in which a metal hull may be protected
including:
– corrosion resistant metals
– development of surface alloys
– new paints
There are several techniques to protect iron and steel from corrosion:
Physical Protection:
Placing a barrier between the water and oxygen and iron can prevent
corrosion
...
polyurethanes and epoxy
resins can do the job
...
Leaching of chemicals can lead to environmental pollution
...

Paints provided the most economical choice, but they do not last
indefinitely
...

Coating with other metals:
This also sets up a physical barrier
...
The tin oxidises to form a protective and stable
oxide layer
...
Galvanised iron is
iron with a layer of zinc
...
Even if this surface is scratched the iron is
galvanically protected
...
Chromium alloy steel forms a passivating layer of
chromium(III) oxide but chromium steels are not very effective against
the chloride ions in sea water, so steel hulls high in nickel content are
preferred
...

Cathodic Protection:
By impressing a small current through the metal it can be protected by
corrosion
...
The paint cures in air forming an impenetrable barrier to both air
and water vapour
...
This
interlayer grows into the neighbouring polymer layer preventing the
crucial movement of ions between the anodic and cathodic areas on the
surface of the steel and so rusting cannot occur
...
Typically, chromium or
nickel ions bombard a steel surface at high temperatures
...

The steel surface forms a passivating layer as the chromium or nickel
reacts with oxygen

• predict the metal which corrodes when two metals form an
electrochemical cell using a list of standard potentials
With two metals in contact, the more active metal forms the anode with
the cathode being the less active metal
...
44 V
2+
Cu (aq) + 2e à Cu (s)
Eø = 0
...
Therefore:
Fe (s) à Fe2+ (aq) + 2eEø = 0
...
34 V
Overall the reaction is:
Fe (s) + Cu2+ (aq) à Fe2+ (aq) + Cu (s)

Eø = 0
...


• outline the process of cathodic protection, describing examples
of its use in both marine and wet terrestrial environments
The basic principle of cathodic protection, is to supply electrons to the
metal structure to suppress metal dissolution
...
Once
connected, these two metals form a galvanic couple
...


• describe the process of cathodic protection in selected examples
in terms of the oxidation/reduction chemistry involved
The two main types of cathodic protection are sacrificial anodes and
impressed electric currents
...
44 V
2+
Mn (aq) + 2e à Mn (s)
Eø = -1
...
34 V
Manganese has the lowest reduction potential, so it can be used to
protect iron and steel structures
...
Mn forms the anode and Fe forms the cathode
...
74 V

The reduction potential of dissolved oxygen is greater than that of iron,
and so the dissolved oxygen is more likely to me reduced
...
52 V

Some electrons may be diverted to reduce iron ions if these form
...

Impressed Electrical Currents:
As long as electrons are supplied to the metal being protected there is no
need to have a sacrificial anode
...
The positive
end of the voltage supply is connected to an inert electrode
...

At the anode water can be oxidised:
2H2O à O2 (g) + 4H+ + 4eEø = -1
...
36 V
Impressed currents are useful for remote locations and large structures,
where it is inconvenient and costly to replace sacrificial anodes
...
These materials included skin and bark, which gave way to wood
...
About 500 years ago, iron nails were used to connect planks
together and to the frame
...

Copper had the advantage of being a biocide, helping against attack by
marine worms and reducing barnacle growth, but the iron nails fastened
to the copper quickly corroded
...

Bronze sheeting eventually replaced copper as it was not expensive and
corroded more slowly
...
g
...

By the late 18th century, most ships weer made from iron, and then steel
...
However it still had advantages over wood
...

Eventually iron gave way to steel, a more versatile, stronger and durable
alloy of iron
...

In recent years, with advances in steel making techniques, a great
variety of super steels can be made with enhanced physical and
chemical properties that are better suited for ship building
...
Obtain strips of metals and alloys such as aluminium, magnesium,
copper, iron, zinc, brass, stainless steel and bronze
...
Add some sea water to partially cover each of the metals in the test
tubes (sea water can be approximated by dissolving 5% w/v NaCl in
water)
3
...
Place a nail in a test tube and cover with ferroxyl indicator
...
In separate test tubes, covered with ferroxyl indicator, place the
following:
• an iron nail tightly wound with copper wiring
• an iron nail tightly wound with magnesium ribbon
• an iron nail painted with phosphoric acid and allowed to dry
• an iron nail painted with outdoor paint
• an iron nail coated with grease
• two iron nails connected by leads to a 1
...
Stressed regions around the tip and head of the control nail should
turn blue, there is less stress around the middle and this should turn
pink
...


• gather and process information to identify applications of
cathodic protection, and use available evidence to identify the
reasons for their use and the chemistry involved
Cathodic protection is the main method for protecting ships’ hulls, oil
rigs
...
The two main
methods involve sacrificial anodes and impressed electrical currents
...
When a ship sinks, the rate of decay and corrosion may be
dependent on the final depth of the wreck
Students learn to:
• outline the effect of:
– temperature
As temperature decreases, the solubility of salts decreases and the
solubility of gases increases

– pressure
As pressure increases, the solubility of salts remains largely
unaffected, and the solubility of gases increases

on the solubility of gases and salts
• identify that gases are normally dissolved in the oceans and
compare their concentrations in the oceans to their
concentrations in the atmosphere
The concentration of most gases in the oceans is lower than their
concentration in the atmosphere
...

The proportion of carbon dioxide in seawater, when compared with
oxygen and nitrogen is higher than its proportion in the atmosphere
when compared to the same two gases
...
The hydrogen ions produced lower the pH of seawater
...

The concentration of oxygen is greatest near the surface because wave
action increases contact between air and water
...
Below 1000m the oxygen
concentration steadily increases as the depth increases
...
1 %
20
...
03 %

Surface Sea Water
62
...
3 %
1
...
8 – 1
...
9 %
4
...
4 %

• compare and explain the solubility of selected gases at increasing
depths in the oceans
Carbon dioxide concentration increases with depth and oxygen
concentration is greatest near the surface and at depth
...
There are a number of other factors that need to be considered
when judging the solubility of gases besides temperature and pressure:
- Photosynthetic rates – the upper regions of the ocean are highly
saturated with oxygen owing to photosynthesis
...
This occurs around polar regions where oxygen-rich water sinks
and spreads over vast distances
...
Much of
this occurs near the surface where most organisms live
- Carbon dioxide reacts with water – the solubility of CO2 in water is
dependent on pH; but it is till 70 times more concentrated in the sea than
in the atmosphere
...
The
breakdown of organic materials also releases carbonates into the
environment
...


• predict the effect of low temperatures at great depths on the rate
of corrosion of a metal
To predict the rate of corrosion at depth you need to consider the
conditions:
- there are very low temperatures, around 4°C

- there are very low oxygen levels (around 2 ppm)
...
From this it an be predicted that corrosion at depth is a
fairly slow process
...


Students:
• perform a first-hand investigation to compare and describe the
rate of corrosion of materials in different :
– oxygen concentrations
– temperatures
– salt concentrations
EXPERIMENT: Comparing corrosion rates in different oxygen
concentrations, temperatures and salt concentrations
AIM: To compare and describe the rate of corrosion of materials in
different oxygen concentration, temperatures and salt concentrations
METHOD: Oxygen Concentrations
1
...
Boil 100mL of this salt water to remove oxygen
...

3
...
Completely fill the
first with the low-oxygen salt water solution and stopper
...
Half fill the third
tube with tap water
4
...
Place tubes to one side to be monitored over several days
METHOD: Temperature Effects
1
...
Place three steel nails separately into test tubes
...
Label the tubes
...
To each test tube add 3 drops phenolphthalein
...
Place one tube in a refrigerator, the second in an incubator and leave
one on the bench top
5
...
Prepare a 150 mL solution of about 3% salt water, also prepare a
solution of about 6% salt water
...
Partly fill the first with the 3% salt water solution
...

Label the tubes

2
...
Monitor the tubes over several says

• use available evidence to predict the rate of corrosion of a metal
wreck at great depths in the oceans and give reasons for the
prediction made

6
...
Scientists were surprised to find that the Titanic had severe
corrosion and they had to revise their theories
...
They are made up of iron hydroxide or iron oxyhydroxide
...
Studies showed
that anaerobic bacteria formed these rusticles
...

They use sulphate ions rather than oxygen to produce energy
...

This is a different process from rusting in shallow waters
...
As the wood decays, it
releases oxygen from the wood cellulose
...
This explains why there is increased
metal corrosion near wood and other organic materials
...
Acidic conditions increase the rate of corrosion in
non-passivating metals
...
The interplay between the two causes greater than expected
corrosion of shipwrecks at great depth
...
The action of
sulphate reducing bacteria reduced the sulphur in the sulphate ion
...
This is
turn makes sea water slightly acidic, thus favouring further corrosion:
Fe (s) + 2H+ (aq) à Fe2+ (aq) + H2
Some of these metal ions can undergo hydrolysis to form more
hydrogen ions, thereby accelerating the corrosion of iron:
Fe2+ (aq) + 2H2O (l) à Fe(OH)2 (s) + 2H+ (aq)
Some sulphate reducing bacteria can also convert hydrogen to hydrogen
ions, and use it to further reduce sulphate ions to hydrogen sulphide
...
40 V

Proceeds more readily in acidic solutions than in neutral or alkaline
solutions
...
23 V

The increase in electrode potential indicates the greater tendency for the
reaction to occur under acidic conditions
The reduction of the sulphate ions forming sulphide are promoted under
acidic conditions:
SO42- (aq) + 10H+ (aq) + 8e- à H2S (aq) + 4H2O (l)
Hydrogen ions can react with non-passivating metals:
Fe (s) + 2H+ (aq) à Fe2+ (aq) + H2 (g)

Non-passivating metals are those which do not form a protective oxide
layer that would prevent hydrogen ions reacting with metal atoms
...
Some
passivating metals include Aluminium, Chromium, Titanium and Tin
...
Prepare six test tubes containing sea water that have been acidified
with a few drops of acid
...
Prepare another set of three test tubes having pH 8
2
...
Label the tubes and observe over several days
RESULTS:
The extent of rusting should be promoted in the test tubes with the lower
pH and inhibited in those with the higher pH

7
...
As well, the cellulose will eventually break down
because of hydrolysis and bacterial action
...

When artefacts are brought to the surface, it is important to keep them
bathed in sea water, or a suitable solution until a decision is made about
treatment
...
X-ray, MRI or ultrasounds may be
employed to determine the exact nature of what is encrusted so a
strategy can be devised for their conservation and restoration
...
Eventually a saturated
solution is produced and any evaporation will cause alt crystals to form
...
The salt crystals can damage the artefact by
placing pressure on the structure, enlarging cracks and pushing it out of
shape
...

Sometimes, the concentrated slats can initiate chemical reactions with
the artefact, further damaging it
...


• identify the use of electrolysis as a means of removing salt
Salts need to be removed from artefacts before they can be conserved
...
The artefact is immersed in a dilute alkaline

solution that is regularly changed over extended periods
...
Over time, anions diffuse
into the artefact replacing the chloride ions, which diffuse out of the
object
...

The concentration of chloride ions in the wash solution can be
monitored using a probe measuring chloride ion concentration
...
This is a very slow process that can
takes months or years
...
This is
because soluble chlorides form insoluble hydroxyl-chlorides with
metals
...
Electrolysis can be used to free the chloride ions from
insoluble compounds into the solution
...
Any residual chloride remaining can cause serious problems as it
can further corrosion, even after the artefact has been cleaned
...


• identify the use of electrolysis as a means of cleaning and
stabilising iron, copper and lead artefacts
Electrolysis is more efficient at removing chloride ions from artefacts
...
A stainless steel mesh surrounds the artefact and is used as the
anode
...
Alkaline
solutions are used for the electrolyte as they discourage further
corrosion
...
Two reactions are possible:
4OH- (aq) à 2H2O (l) + O2 (g) + 4e2H2O (l) à 4H+ (aq) + O2 (g) + 4eMetal ions in the corrosion products are reduced to metal atoms and
deposit on the artefact:
Fe(OH)2 (s) + 2e- à Fe (s) + 2OH- (aq)
Fe(OH)Cl (s) + 2e- à Fe (s) + OH- (aq) + Cl- (aq)

Chloride and hydroxide ions migrate out of the artefact towards the
anode
...

Electrolytic reduction can take days or weeks to complete
...


• discuss the range of chemical procedures which can be used to
clean, preserve and stabilise artefacts from wrecks and, where
possible, provide an example of the use of each procedure
The procedure used to preserve an artefact depends on a number of
factors such as the type of material, its size, and state of decay
...
Tis is done
physically, by chipping with chisels or chemically by soaking in dilute
acid solutions
...
The strength of the wood can be severely
compromised
...

Electrophoresis: some ceramic and organic matter may have picked up
salts and dirt
...
This may be enough to
cause dirt particles to migrate to one of the electrodes
...
This reducing atmosphere of hydrogen
converts iron chlorides and iron oxides to iron:
FeO (s) + H2 (g) à Fe (s) + H2O (g)
Cleaning copper artefacts: in aerobic environments copper can be
slowly oxidised to form Cu4(OH)6Cl2 and hydrochloric acid
...
One way to clean these corrosion layers is to
dissolve them in dilute citric acid solution
‘Bronze diseases’ occurs when CuCl within the bronze artefact reacts
with moisture forming a hydroxyl compound
...
The chloride

in CuCl can be removed by hydrolysing in a solution of
Na2CO3/NaHCO3
Cleaning silver artefacts: In aerobic environments surface silver may
form AgCl and AgBr
...
These corrosion products can be cleaned
using electrolytic reduction
...
The cathode reaction is:
Ag2S (s) + H2O (l) + 2e- à 2Ag (s) + HS- (aq) + OHCleaning lead artefacts: In aerobic environments surface lead may form
PbSO4, whereas PbS is the product under anaerobic conditions
...
The cathode
reaction is:
PbS (s) + H2O (l) + 2e- à Pb (s) + HS- (aq) + OH- (aq)
Finally the artefact needs to be sealed to preserve it
...


Students:
• perform investigations and gather information from secondary
sources to compare conservation and restoration techniques
applied in two Australian maritime archaeological projects
Vernon Anchors:
• concretions and paint remains were removed and surface was coated:
- iron surface: blasted with copper slag, then garnet polish
...
Iron was then treated with a zinc epoxy paint to
create a protective layer
- timber stocks : saturated with zinc napthenate solution, as it retards
growth of organisms, but causes a green decolouration so was not
used on anchor
• anchors were displayed outside, so a mounting system was built,
including aluminium mesh on which the anchors rest:
- mesh rather than solid metal allows water to drain away, and a build
up of water can cause corrosion
- aluminium was chosen because of its electrode potential relative to
iron
• anchors are regularly inspected for deterioration and the anchors are
hose with freshwater on a regular basis to reduce salt build up, as
they are on display near the water
HMS Sirius Anchor:
• photographs were taken and corrosion potentials measured before it
was taken from the water; it was transferred from the sea to s tank
filled with rain and creek water, and concrete blocks were placed in
the tank to stop the anchor from making contact with the tank
• a small area of concretion was removed and a cathode rod was
inserted, the rest of the concretions were removed with a hammer and
chisel
• a 15mm fissure was found in the anchor, which allowed a build up of
moisture, a hole was drilled to encourage diffusion of salts and
drainage of moisture
• anchor was placed in tank with water and caustic soda as treatment
and anode sheets were placed in the tank
• recordings indicated the anchor was stable and salt was diffusing
...
A clear
lacquer was used as it is on display inside, so it is not in contact with
the outside, and it best reserves its appearance
• wooden stocks were added to display the anchor in the museum and
to illustrate its function



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