Chemistry: Chemical Monitoring & Management1 Monitoring and Managing Reaction Conditions1.1Outline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining the chemical principle that the chemist uses:Robert Evans: Robert Evans is an environmental chemist. He is employed by Orica Ltd, and works at Botany Industrial Park, Sydney.Role: The management of disposal of contaminated wastes (such as neutralising strongly acidic or basic wastes, or incinerating toxic wastes) Investigating reports of contamination in soil or groundwater, determining the source of contamination, and then correcting the damage.Chemistry: Chemical principles needed for this role include: Understanding acid/base reactions (neutralising wastes) Knowing valid chemical sampling techniques Various techniques of chemical analysis of samples, including gravimetric and volumetric analysis, as well as AAS (atomic absorption spectroscopy)

1.2Identify the need for collaboration between chemists as they collect and analyse data: Chemists tend to specialise within a particular branch In real-life situations, many chemical problems require expertise and in depth knowledge from a wide range of chemical branches Hence, collaboration between chemists is essential for solving chemical issues, as the chemists provide input and expertise from their own particular field, for a common goal

1.3Describe an example of a chemical reaction such as combustion, where reactants form different products under different conditions and thus would need monitoring: Combustion: Chemical reactions can form different products under different conditions. Take, for example, the combustion of a simple hydrocarbon, propane. In an environment with adequate amounts of oxygen, propane combusts completely, forming only carbon dioxide and water: propane + oxygen carbon dioxide + waterC3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (g) In an environment with insufficient oxygen, propane combusts incompletely, and can form a range of different products, such as carbon (soot), carbon monoxide, and water. propane + oxygen carbon + carbon monoxide + waterC3H8 (g) + 3O2 (g) C (s) + 2CO (g) + 4H2O (g) Monitoring: Hence, under different conditions, chemical reactions can proceed in different ways, as seen by the combustion reaction above. However, in certain situations (such as in car engines), only one reaction is desired. Thus, the reaction conditions must be monitored to ensure that only (or mostly) the wanted reaction occurs. Carbon monoxide is a poisonous gas and can affect human health negatively. Carbon (soot) is carcinogenic (causes cancer) to humans and can be irritating to the lungs. Both of these alternative products can also signal a decrease in fuel efficiency and result in a reduced energy yield from the fuel.

1.4 Gather, process, and present information from secondary sources about the work of practising scientists identifying; the variety of chemical occupations & a specific chemical occupation for more detailed study:The Variety of Chemical Occupations: The large range of jobs available in the chemical industry includes: Analytical chemistry, Bio-molecular chemistry, Colloid and surface science chemistry, Environmental chemistry, Industrial chemistry, Inorganic chemistry, Electrochemistry, Organic chemistry, Physical chemistry, Polymer chemistry.A Specific Chemical Occupation: A summary of the job of an environmental chemist: Job includes reviewing operation of effluent water treatment systems and ensuring compliance with government environmental regulations. Assessing levels of potential contamination in wastes (e.g. soil) intended for landfill disposal and classifying them in accordance with government guidelines. Managing disposal of contaminated wastes. Investigating reports of contamination in soil or groundwater to determine source and then arranging to correct it.

2 Monitoring and Management to Maximise Production2.1Identify and describe the industrial uses of ammonia: Ammonia (NH3) is industrial used as solid and liquid fertilisers, household cleaners, explosives and some pharmaceuticals. Fertilisers: through a reaction with sulfuric acid or nitric acid to form ammonium sulfate fertiliser or ammonium nitrate fertiliser. Household cleaners: ammonia solution (ammonium hydroxide) kills bacteria

2.2Identify that ammonia can be synthesised from its component gases, nitrogen and hydrogen: The synthesis of ammonia from hydrogen and nitrogen (the Haber process): N2(g) + 3H2(g) 2NH3(g)

2.3Describe that synthesis of ammonia occurs as a reversible reaction that will reach equilibrium: The synthesis of ammonia occurs as a reversible reaction; i.e. ammonia is formed from nitrogen and hydrogen (the forward reaction) and once some ammonia is produced, some nitrogen and hydrogen are formed from the ammonia (the reverse reaction). When nitrogen and hydrogen are initially added to a 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.

2.4Identify the reaction of hydrogen with nitrogen as exothermic: N2 (g) + 3H2 (g) 2NH3 (g)H = 92 kJ From the equation we can see that H is negative; hence, the reaction is exothermic.

2.5Explain why the rate of reaction is increased by higher temperatures: As temperature is increased, energy is delivered into the reaction as thermal energy. This thermal energy is converted into kinetic energy, and particles begin to move faster. This causes more collisions between particles, and hence more reactions occur. Also, if the temperature is higher, there is more chance that colliding particles will have the necessary activation energy for the reaction to take place.

2.6Explain why the yield of product in the Haber process is reduced at higher temperatures using Le Chateliers principle: The forward reaction in which ammonia is formed is exothermic (heat produced) Le Chatelier's principle states that if a system in equilibrium is disturbed, the system will adjust itself to minimise the disturbance. In this case, Le Chatelier's principle indicates that with high temperature providing more heat, the reverse reaction is favoured and the decomposition of ammonia occurs, thus decreasing the yield of ammonia.

2.7Explain why the Haber process is based on a delicate balancing act involving reaction energy, reaction rate and equilibrium: In order for the Haber process to be economically viable, we need to consider yield of products, rate of reaction, as well as costs. Hence, a compromise (balancing act) of all the above must be made: Temperature: Higher temperatures will produce ammonia faster, but lower temperatures will produce more ammonia. Hence a moderate temperature of about 400-500oC is used, together with the iron/iron-oxide catalyst. Pressure: Increased pressure will produce more ammonia, also faster, but it will be expensive to build and maintain high-pressure equipment. The benefits of high pressure outweigh the costs, and so a pressure of 250-350 atmospheres is used.

2.8Explain that the use of a catalyst will lower the reaction temperature required and identify the catalyst(s) used in the Haber process: With the use of catalyst, the activation energy for the reaction is reduced. A finely ground iron oxide (magnetite; Fe3O4) catalyst, with large surface area, is used in the Haber process. By lowering the activation energy, a catalyst enables a more rapid reaction at lower temperatures.

2.9Analyse the impact of increased pressure on the system involved in the Haber process: N2 (g) + 3H2 (g) 2NH3 (g) According to Le Chateliers principle, increasing the pressure will favour the side that will reduce the pressure (i.e. has LESS moles of gas): In this reaction, there are less moles of gas on the product side (gas ratio is 4:2) and hence increasing the pressure will favour the production of ammonia. In addition, higher pressures also increase the reaction rate because the gas molecules are closer and at higher concentrations.

2.10Explain why monitoring of the reaction vessel used in the Haber process is crucial and discuss the monitoring required: Monitoring is needed to maintain optimum conditions for optimum yield (around 30%) with the least possible waste. The raw materials must be monitored to ensure they are clean. Monitoring the reaction vessel to ensure that the appropriate temperature and pressure conditions are maintained. The quality of the catalyst surface needs to be monitored to ensure good adsorption of the nitrogen and hydrogen gases. The system must be kept free of contaminants to ensure maximum surface of the catalyst is available for adsorption of nitrogen and hydrogen.

2.11Gather and process information from secondary sources to describe the conditions under which Haber developed the industrial synthesis of ammonia and evaluate its significance at that time in world history: The development of the industrial synthesis of ammonia: Fritz Haber: Haber succeeded in making small amounts of ammonia from hydrogen and atmospheric nitrogen in the laboratory. He discovered a catalyst for the reaction and worked out the conditions of temperature and pressure that allowed a reasonable yield. Carl Bosch: Bosch developed the process to an industrial scale, including inventing the necessary high pressure technology that would enable the process to be carried out on a large scale. The conditions used by Haber and Bosch to allow the production of commercial quantities of ammonia: Nitrogen and hydrogen used in ratio of 1:3 250-350 atmospheres pressure about 450oC temperature catalyst of finely divided iron or iron oxide ammonia liquefied and removed as it is produced The significance of the industrial synthesis of ammonia: Before the invention of the industrial Haber process in 1913, the global source of nitrates (for fertilisers and explosives) came from saltpetre (bird poo/guano) from Chile. During WWI, Germanys supplies of nitrogen compounds were cut off by the British; this threatened to cause widespread starvation, as well as cause Germany to rapidly lose the war (they relied on saltpetre to make explosives). Historians believe that Germany would have run out of nitrates by 1916 if it had not developed the Haber process. On the other hand, the Allies had to rely on Chilean nitrates, which became more expensive as the war progressed. However, with the invention of the Haber process, Germany (and later the rest of the world) had a cheap source of nitrates from elemental nitrogen and hydrogen. Thus, the Haber-Bosch process had a significant impact on the course of history during the early 20th century as it allowed Germany to continue the war for much longer than otherwise would have been possible.

3 Analysing Manufactured Products3.1Deduce the ions present in a sample from the results of tests: We use precipitation reactions to identify ions in solution: Cation identification:

Anion identification:

3.2Describe the use of atomic absorption spectroscopy (AAS), in detecting concentrations of metal ions in solutions and assess its impact on scientific understanding of the effects of trace elements:

Cathode

Atomic absorption spectroscopy (AAS) is a method of quantitatively determining the concentrations of metal ions in solutions; it is extremely sensitive, usually measures in ppm.How it works: The flame containing the vapourised sample absorbs light at the particular wavelengths characteristic of the element in the flame and re-emits it in all directions. A detector records the intensity of light emerging from the flame. The intensity of light detected drops sharply at the wavelengths of light absorbed by the elements in the flame, thus producing an absorption spectrum. The relative intensity and pattern of changes of intensity within each of the bands in the absorption spectrum indicate the concentration of the element in the test sampleImpact on scientific understanding of the effects of trace elements: Trace elements are elements that are needed in minute amounts by living things - for the proper growth, development, and physiology of organisms. The presence of these elements were often unnoticed, and the causes of diseases relating to trace-element deficiency (such as goitre; iodine deficiency) were unknown. AAS enabled the measurement of the concentrations of many elements in organisms, showing that not only that there were trace amounts of elements in all organisms, but that these were also essential for their well-being. Hence, AAS had a great impact on the understanding of trace elements.

3.3Gather, process and present information to describe and explain evidence for the need to monitor levels of specific ions in substances used in society:Summary of information gathered

Identify the ion chosenLead

Why the ion needs to be monitored Lead is a toxic, heavy metal and a neurotoxin Can cause damage to all organisms in the body, especially the brain, kidneys and reproductive system. It disrupts enzyme systems and causes anaemia as it inhibits the formation of red blood cells. Causes brain damage and retards intellectual development in young children. Lead bioaccumulates and is difficult to eliminate Bioaccumulation occurs along the food chain so levels can build up in animals at the end of chains, i.e. humans

How the ion is monitoredLead is readily detected and its concentration is measured by AAS

Substances monitored for this ion atmosphere waters food human tissues soil

Sources of the ion in these substances Mining and refining of ores containing lead (i.e. copper smelters) Paints containing lead released as it deteriorates or is sanded or burnt Lead glazing of pottery Corrosion of plumbing materials containing lead Car batteries Burning of rubbish

Incidents involving this metalHigher concentrations of lead in the atmosphere along major roads, when lead was allowed in petrol, and around mining towns and copper smelting, caused lead poisoning. Children with higher than normal lead concentrations in blood after eating flaking paint in their homes.

4 Human Activity and the Atmosphere4.1Describe the composition and layered structure of the atmosphere: The atmosphere is predominantly composed of nitrogen (78% by volume), oxygen (21%), and argon (0.93%), with the other gases in very small concentrations.

4.2Identify the main pollutants found in the lower atmosphere and their sources:PollutantMain Sources

Carbon monoxideIncomplete combustion in stoves, cars, fires and cigarettes

Nitrogen oxidesCombustion at high temperatures in vehicles and power stations

Volatile organic compounds; such as hydrocarbonsUnburnt fuel, solvents and paints

Sulfur dioxideSome metal extraction processes and the burning of fossil fuels

LeadLeaded fuels, metal extraction, renovating old houses containing leaded paints

Carbon dioxide (CO2)Combustion of fossil fuels in motor vehicles and electricity production

Particulates (soot, asbestos, etc.)Incomplete combustion, earthmoving dust storms and some agricultural and industrial practices

4.3Describe ozone as a molecule able to act both as an upper atmosphere UV radiation shield and a lower atmosphere pollutant: The ozone molecules in the stratosphere (upper atmosphere) form a very thin layer that protects us from harmful UV radiation. In contrast, the ozone in the troposphere (lower atmosphere) is a pollutant, even at the very low concentrations compared with the other gases. Ozone is a very reactive molecule capable of oxidising many substances.

4.4Describe the formation of a coordinate covalent bond: Non-metallic compounds contain covalent bonds. A covalent bond is a shared pair of electrons that keeps two atoms together. A coordinate covalent bond forms when one atom in a species (a molecule or ion containing non-metallic atoms) provides both electrons in the covalent bond.

4.5Demonstrate the formation of coordinate covalent bonds using Lewis electron dot structures: Ions, such as the hydronium H3O+ and the ammonium NH4+, contain a coordinate covalent bond. In the formation of the hydronium ion, one of the non-bonding electron pairs on the oxygen atom is used to form a covalent bond between the hydrogen ion H+ (which has no electrons) and the oxygen atom. Formation of a coordinate covalent bond in the hydronium ion:

Formation of a coordinate covalent bond in the ammonium ion:

4.6Compare the properties of the oxygen allotropes O2 and O3 and account for them on the basis of molecular structure and bonding: An allotrope is a different physical form of the same element; e.g. O2 and O3 are allotropes of oxygen.

PropertyO2 (oxygen gas)O3 (ozone)Explanation

State and colourColourless gasPale blue gas-

OdourOdourlessSharp, pungent odour-

Boiling point183oC110oCThe boiling point of diatomic oxygen is lower than that of the ozone as diatomic oxygen has a lower molecular mass requiring less energy in the boiling process.

ReactivityModerately reactive.Decomposed by high energy UV light.Highly reactive.Decomposed by medium energy UV light.To decompose oxygen, its double bond has to be broken; this requires considerable amounts of energy. However, the single bond (coordinate covalent bond) in ozone requires much less energy to be broken, and hence ozone is much less stable (readily decomposes to O2).

Oxidation abilityModerately strong oxidising agentVery strong oxidising agent. The oxidising strength of ozone comes from the weakness of the single bond; it easily releases an oxygen atom which can then oxidise a compound.

Solubility in waterSlightly soluble15 times more soluble than oxygenNon-polar O2 does not form strong intermolecular forces in the polar water. Ozone has a bent structure, which provides for some polarity of the molecule in its interaction with water.

Structure and bondingDiatomic molecule; two oxygen atoms held together with a covalent double bond.Three oxygen atoms held together with 1 double covalent bond and 1 single coordinate covalent bond-

ShapeMolecule is linear shape. Thus, non-polar.Molecular shape is bent polar molecule-

4.7Compare the properties of the gaseous forms of oxygen and the oxygen free radical: A free radical is a reactive particle that contains one or more unpaired electrons in its outer shell. E.g: The oxygen free radical: O2 2O The oxygen free radical has two pairs of electrons, as well as two unpaired electrons (see diagrams); these unpaired electrons are highly reactive.

O2, O3 and the oxygen free radical (O) are all forms of the element oxygen, but the free radical is much more reactive and the most toxic. In order of reactivity, the diatomic oxygen molecule is less reactive than the ozone molecule, which is less reactive than the oxygen free radical.

4.8Identify the origins of chlorofluorocarbons (CFCs) and halons in the atmosphere: Chloroflurocarbons (CFCs) are halogenated alkanes with all hydrogens substituted with chlorine and fluorine atoms CFCs were very widely used as: Refrigerants/coolants in fridges and air-conditioners Propellants in aerosol spray cans Foaming agents in the manufacture of foam plastics like polystyrene Cleaning agents in electronic circuitry Solvents in dry cleaning These many uses released CFCs directly into the lower atmosphere. Halons are halogenated alkanes with hydrogens substituted with bromine in addition to chlorine and fluorine atoms They are dense, non-flammable liquids that were widely used as effective fire-extinguishersbecause of their excellent fire retardant properties. As they were used onto fires, the halons were released directly into the atmosphere Because both halons and CFCs are so inert, they remain in the atmosphere unchanged for many years

4.9Identify and name examples of isomers (excluding geometrical and optical) of haloalkanes up to eight carbon atoms: A haloalkane is an alkane with one or more halogen (elements in group 7) atoms replacing hydrogen atoms. Isomers are molecules with the same molecular formula but different structural formulas (arrangements of atoms). The longer the carbon chain, the more possible isomers there will be.

4.10Discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems:The biggest problem associated with the use of CFCs is the depletion of the ozone layer and enhancing the greenhouse effectDepletion of the ozone layer: CFCs are very inert, and are not washed out by rain. CFCs remain in the troposphere for many years, because they are very stable, and eventually diffuse into the stratosphere. CFCs are broken down by the presence of UV radiation in the atmosphere (photo dissociation), releasing halogen free radicals. These free radicals can then react with ozone, destroying it. This increases the UV radiation penetrating the Earth, leading to: increases in sunburn and skin cancer damage to plants and decreases in crop productivity the breaking down of chemical bonds, in particular in biological polymers like DNA and proteins, causing considerable damage to living systemsThe greenhouse effect: The greenhouse effect is the heating of the Earth as a consequence of some gases in the atmosphere which absorb and emit infrared radiation. Without these gases, heat would escape and Earths average temperature would be much colder. Gases that warm the Earth (such as CFCs) are greenhouse gases. There are worries that all of the extra greenhouse gases being generated because of human activities might increase the greenhouse effect, leading to global warming.

Dealing with the CFC problem: The only way to stop ozone depletion is to STOP releasing CFCs of any form. International agreements based on the common goal of phasing out CFCs are being used. The Montreal Protocol on Substances That Deplete the Ozone Layer (1987) - ceasing the manufacture and banning the use of CFCs CFC Replacements - Finding alternative compounds to fulfil the roles of CFCs is a major step forward in preventing ozone depletion. Alternatives include; replacing CFC aerosols propellants with hydrocarbons and the use of normal pressure packsEffectiveness of These Solutions: The Montreal Protocol is only effective if member nations adhere to its regulations; so far, the Montreal Protocol has been a huge success in international agreement and environmental health. Certain CFC replacements are not as effective as the CFCs themselves; future technological advancement hopes to find better replacements. There are still, however, significant levels of CFCs in the atmosphere, and current technology has no way of removing them.

4.11Analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and explain how this information was obtained: How Are Ozone Levels Measured? Stratospheric ozone levels are measured by spectrophotometers in ground-based instruments, instruments in satellites and instruments in weather-balloons. The measurements made indicate that changes in ozone levels have occurred. The Changes Observed: Measurements of the total amount of ozone in a column of atmosphere have been recorded since 1957. The main depletion of ozone has occurred over the Antarctic. Scientists identified that a dramatic decline in springtime ozone occurred from the late 1970s over the entire Antarctic. The decline reached approximately 30% by 1985. In some places, the ozone layer had been completely destroyed. The ozone decline over Antarctica during springtime is now not so dramatic, but often exceeds 50%.

4.12Present information from secondary sources to write the equations to show the reactions involving CFCs and ozone to demonstrate the removal of ozone from the atmosphere:CFCs can undergo photodissociation (reactions using the energy of light to break bonds) to form reactive chlorine atom radicals (Cl). The chlorine atom radical then rapidly reacts with an ozone molecule to produce the chlorine oxide molecule, ClO. The chlorine oxide molecule can react with a free oxygen atom (which could have formed O3 by reaction with O2) regenerating a Cl atom. Formation of chlorine radical: CCl2F2 (g) + UV radiation Cl (g) + CClF2 (g) Reaction of ozone: Cl (g) + O3 (g) ClO (g) + O2 (g) Regeneration of chlorine: ClO (g) + O (g) Cl (g) + O2 (g)

4.13Present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs: Ammonia: Large scale (industrial) refrigeration has reverted back to using ammonia as a refrigerant, as was done prior to the discovery of CFCs. Effectiveness: Ammonia is an environmentally friendlier alternative to CFCs, but great care must be exercised, as ammonia is dangerous and toxic. HCFCs: Hydro chlorofluorocarbons are CFCs that contain hydrogen. HCFCs replaced CFCs in domestic refrigeration, as propellants in spray cans, as an industrial solvent and as a foaming agent. Effectiveness: Smaller amounts of HCFCs do reach the stratosphere, and hence they are also ozone-depleting (10% the ozone-depleting potential of CFCs). They are seen as only a temporary solution. HCFCs also contribute massively to the greenhouse effect, and so their use is being phased out. HFCs: Hydro fluorocarbons are compounds that contain only carbon, hydrogen and fluorine (no chlorine or bromine). HFCs are very widely used in refrigeration and air-conditioning applications. Effectiveness: As they have zero ozone-depleting potential, HFCs are a good alternative to using CFCs in terms of atmospheric health. However, they are not as effective refrigerants as CFCs, and are slightly more expensive. They are also strong greenhouse gases, and so further research is required.

5 Monitoring and Management in Water5.1Identify that water quality can be determined by considering; concentrations of common ions, total dissolved solids, hardness, turbidity, acidity, dissolved oxygen and biochemical oxygen demand:Water quality can be determined by considering the following factors:Concentrations of common ions: Some ions are essential to aquatic life, and can greatly affect the water qualityTotal dissolved solids (TDS): High concentrations are usually uninhabitable for many speciesHardness: Hard water can help prevent metals leaching from old pipes into the water supply, but can also block the flow of water from build up of scumTurbidity: High turbidity reduces the penetration of sunlight, reducing the effectiveness of aquatic plants photosynthesisAcidity: Drinking water should have a pH between 6.5 and 8.5Dissolved oxygen: Low oxygen levels in water can lead to the death of aquatic organismsBiochemical oxygen demand: High BODs indicate significant levels of organic pollution

5.2Identify factors that affect the concentrations of a range of ions in solution in natural bodies of water such as rivers and oceans:Factors include: the frequency of rainfall (floods and droughts) water temperature evaporation rates soil type pollution sources, such as the presence of animal faeces and fertiliser usage land use

5.3Describe and assess the effectiveness of methods used to purify and sanitise mass water supplies: Monitoring Catchment: The first step to ensure water used for human use is clean is to ensure that the area the water flows over (the catchment area) is kept clean. This involves banning any land-clearing, swimming, boating, industry and agriculture in the entire catchment area, to prevent sediment, animal waste or bacteria to build up in water supplies. EFFECTIVENESS: This is a very cheap and effective way of ensuring the purity of water for human use; by removing the sources of contamination, purity is ensured. Filtration: Filtrating the water through sand and gravel beds. EFFECTIVENESS: Relatively cheap, although does not remove many small particles

Flocculation: Some suspended particles (called colloidal particles) cause water to become turbid, but are too small to be removed by conventional filtration. During flocculation, chemicals, such as iron (III) chloride and aluminium hydroxide and a cationic polymer, are added to coagulate the fine particles together, forming larger particles, which can then be removed by filtration. EFFECTIVENESS: Flocculation removes most of the suspended particles, as well as bacteria, which are caught up in the particle aggregates. It is very cost-effective, and relatively fast. Chlorination: Because of their oxidising ability, chlorine and hypochlorites are used extensively in sterilising swimming pool water and the treatment of waste water. EFFECTIVENESS: Chlorination is an effective way of killing most micro-organisms Chlorine may impart an unpleasant odour on the water

5.4Describe the design and composition of microscopic membrane filters and explain how they purify contaminated water: Microscopic membrane filters have microscopic pores and the use of appropriate sized filters can avoid the need to chemically treat the water. The filters can be classified as microfiltration, ultrafiltration or nanofiltration, depending on the size of the pore. The membrane is made from synthetic polymers dissolved in a mixture of solvents. Water-soluble powders of a particular size are added. The mixture is spread out over a plate and left for the solvent to dry. The polymer membrane formed, containing particles of water-soluble powder, is then placed in water. Remaining solvent and the powder particles dissolve, leaving a very thin polymer sheet with definite sized microscopic pores where the water-soluble particles were located. Water is made to flow across the membrane not through it; reducing the blockage factor. The size of the pore determines which sized particle or organism may pass through the membrane. The finer the pore size the smaller the particles trapped and the more expensive the membrane.

5.5Gather, process and present information on the range and chemistry of the tests used to; identify heavy metal pollution of water & monitor possible eutrophication of waterways:Heavy metal pollution of water: Heavy metals refer to metals with large atomic masses The heavy metals that are of the most concern due to their extremely detrimental effects on health are mercury, lead, cadmium, chromium and arsenic. Methods to test for heavy metals: Quantitative: AAS: very sensitive, quick and accurate samples need to be sent to a lab Chemistry: absorbance of the atomised water sample is measured at specific wavelengths. Each wavelength is selected to measure one element in the mixture. The absorbance is related to concentration using a calibration curve. Qualitative: Precipitation tests can be used in the field, when an immediate indication is required, not as sensitive as AAS Chemistry: precipitation tests utilise the varying solubility of ionic compounds i.e. add KI to form a yellow precipitate of PbI2, indicating lead contamination Flame tests

Eutrophication: Eutrophication involves an increase in the nutrients in water, leading to excessive algal growth, followed by the decay of the organisms and depletion of oxygen in the water. Methods to test for eutrophication: Measuring the nitrogen and phosphorous content of the water by colorimetric tests Chemistry: the nitrates or phosphates are converted to coloured compounds using standard reagents. The depth of the colour is measured and converted to concentration units with a calibration curve. Measure turbidity turbidity increases as algae grow Chemistry: turbidity is measured by the light that can penetrate a solution. Attach a faint black cross to the base of a long colourless cylinder. Look down the tube. Slowly pour in the water until the cross disappears. Measure D.O. (dissolved oxygen) and B.O.D. (biochemical oxygen demand) D.O. will decrease and B.O.D. will increase as the algae die Chemistry: D.O. and B.O.D. are measured by data loggers and an oxygen probe. The probe sets up an electrochemical cell with the oxygen and a voltage is generated that is proportional to the oxygen content.

5.6Gather, process and present information on the features of the local town water supply in terms of; catchment area, possible sources of contamination in this catchment, chemical tests available to determine levels and types of contaminants, physical and chemical processes used to purify water, chemical additives in the water and the reasons for the presence of these additives:For the local Sydney area, the water is supplied by Warragamba Dam.Catchment area: Warragamba Dam is Sydney's main water storage dam, and one of the largest domestic water supply dams in the world. Catchment areas are areas of land from which rain water drains toward a common water-body - the Warragamba catchment has an area of about 9000 km2 Sources of contamination: Land Clearing: Within the catchment area, there are various logging and land-clearing activities occurring to make way for more agricultural land leading to higher turbidity Agriculture: There are various patches of land within the catchment area that are used for agricultural purposes such as growing crops or raising cattle this contamination leads to the growth of bacteria, as well as a high B.O.D. Mining: Within the catchment area are abandoned mines which water can flow into out of; leaching out with certain ions such as Zn2+, Cu2+ and sulfides from the metal ores, which make the water acidic. Natural Soil: The natural soil and rock around the catchment area have high levels of iron and manganese in them; rain water can leach out these minerals, in the form of Fe3+ and Mn2+ ions leads to water with a coloured tinge and a metallic taste.

Animals: Certain feral and native animals may contaminate the water with their faeces directly, or by dying and decaying within the water can lead to serious contamination of the water.Testing for contaminants: Most chemical tests are used to detect the levels common ions, and ensure that they remain below safe thresholds. [See above for types of chemical tests, including; AAS, colorimetric tests, etc.]Water purification: Water is first screened to remove large debris; flocculation then occurs using Fe3+or Al3+ electrolytes, followed by shaking to encourage precipitate formation; this is then left in a sedimentation tank to settle; sludge is scooped out and the clean water is led onto a sand-bed filter; this filter consists of layers of sand and gravel and the water comes out clean.Chemical additives: The 2 main chemical additives in Sydney water are chlorine and fluoride. Chlorine (Cl2) is added to the water supply as a disinfecting agent; chlorine gas is bubbled through the water just before it exits the plant. Hypochlorite ions are formed, and these kill bacteria and some viruses, sanitizing the water. Fluoride (F-) is added to the water because it is believed to strengthen tooth enamel in growing children. Fluoride ions are added in the form of sodium fluoride at a controlled concentration of 1 ppm.

Practicals to cover:

(3.) 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 and iron.

(3.) Identify data, plan, select equipment and perform first-hand investigations to measure the sulfate content of lawn fertiliser and explain the chemistry involved.

(3.) Analyse information to evaluate the reliability of the results of the above investigation and to propose solutions to problems encountered in the procedure.

(4.) Gather, process and present information from secondary sources including simulations, molecular model kits or pictorial representations to model isomers of haloalkanes.

(5.) Perform first-hand investigations to use qualitative and quantitative tests to analyse and compare the quality of water samples.

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