Chemical Monitoring and Management

Chemical Monitoring and Management2013

Contextual OutlineThe state of our environment is an important issue for society. Pollution of air, land and water in urban, rural and wilderness areas is a phenomenon that affects the health and survival of all organisms, including humans. An understanding of the chemical processes involved in interactions in the full range of global environments, including atmosphere and hydrosphere, is indispensable to an understanding of how environments behave and change. It is also vital in understanding how technologies, which in part are the result of chemical research, have affected environments. This module encourages discussion of how chemists can assist in reversing or minimising the environmental problems caused by technology and the human demand for products and services. Some modern technologies can facilitate the gathering of information about the occurrence of chemicals both those occurring in natural environments and those that are released as a result of human technological activity. Such technologies include systems that have been developed to quantify and compare amounts of substances. This module increases students understanding of the nature, practice, applications and uses of chemistry and the implications of chemistry for society and the environment.

1. Much of the work of chemists involves monitoring the reactants and products of reactions and managing reaction conditionsStudents Learn To: outline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist usesMaria Skyllas Kazacos is an electrochemist. She was the inventor of the Vanadium Redox Battery which was developed at the UNSW during 1980s and 1990s. It is now commercialised around the world in a wide range of energy storage applications. It is a rechargeable battery.Named EnterpriseDevelopment of the Vanadium redox batteryBranch of ChemistryElectrochemistryChemical PrincipleBatteries work by using spontaneous oxidation reduction reactions to produce a flow of electricity identify the need for collaboration between chemists as they collect and analyse dataCollaboration means the sharing of ideas, facilities and resources. Chemists work in teams. Some will have particular expertise and roles in the task at hand. Some may have expertise in and access to special technology, others in understanding previous work, others in analysis of new data and so forth.International collaboration in science and technology is therefore natural, especially as many problems that need scientific/technological solutions (eg. Pollution, spread of disease, climate change) do not respect national frontiers.This means that collaboration is a vital aspect of the collection and analysis of data. Collaboration avoids unnecessary duplication of research or equipment (eg. Large Hadron Collider of CERN), can reduce costs and maximise the knowledge base and peer review and assessment available for a specific task.International CollaborationAdvantages: Save time (no need to repeat something another scientist has done, gains information from experts in another branch) Save cost (no need to duplicate expensive equipment, the money can be used for other purposes) Ideas (discussion and contact can stimulate thoughts, different people think differently, better problem solving and more effective data analysis) May be needed to reach critical mass of expertise and/or resources Whole > sum of partsDisadvantages: Reduces diversity + spur of scientific competition Tension between competition and collaboration Added complexity of decision making describe an example of a chemical reaction such as combustion, where reactants form different products under different conditions and thus would need monitoring Maximum amount of desired product formed, unwanted products minimised Reaction goes to completion, not coming to an unfavourable equilibrium Reaction rates need to be reasonably quick in order to produce products quickly No pollutants produced either from the reactants itself or the impurities in the starting materials If the reaction is being used to generate energy, the maximum amount of energy be produced Cost, must be economically viable. Is it cheaper to use more energy or a catalyst to speed up the reactionCombustion of a gas (CH4 or C3H8) in a Bunsen burner needs monitoring. High temperature flame, air hole fully open, sufficient oxygen reaches the fas for complete combustionCH4(g) + 2O2(g) => CO2(g) + 2H2O(g)[methane]C3H8(g) + 5O2 => 3CO2(g) + 4H2O(g)[propane]

Air hole partly open, incomplete completion occurs, producing carbon monoxide2CH4(g) + 3O2 => 2CO(g) + 4H2O(g) [methane]2C3H8(g) + 7O2(g) => 6CO(g) + 4H2O(g)[propane]

Air hole closed, carbon produced. Heated carbon gives low temperature flame yellow colourCH4(g) + O2(g) => C(s) + 2H2O(g)[methane]C3H8(g) + 2O2(g) => 3C(s) + 4H2O(g) [propane]

Adjusting the fuel-to-air ratio is important in internal combustion engines and in industrial combustion of fuels. The more complete the combustion, the greater the amount of energy released. Incomplete combustion produce poisonous COThe products of combustion are determined by the amount of oxygen present. Eg Car Engine:2C8H18(l) + 10O2(g) => 16CO(g) + 18H2O(l)[complete]2C8H18(l) + 13O2(g) => 8CO(g) + 8C(s) + 18H2O(l)[incomplete]Combustion must be monitored to ensure there is sufficient oxygen for complete combustion because CO is poisonous and is absorbed by human blood more readily than oxygen, cause death Build-up of soot in engines and exhaust systems cause inefficiency Soot and smoke are pollutants to the atmosphere Complete combustion releases more energy than incomplete combustionModern cars have catalytic converters that reduce the emissions using various catalysts. Electronic fuel injections are computer controlled devices that control the fuel-air mixture to ensure complete combustion. Students: 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 a more detailed studyBranchDescription

Environmental chemistryDetermines how substances interact in the environmentMonitoring concentrations of substances (pollutants) in air, water, soil

Polymer chemistryDeveloping new polymers with particular propertiesStudying polymerisation and how it can be more efficientStudying properties of polymers

Industrial chemistryChemistry of industrial processes such as manufacturing of compounds

Food chemistryPreservation and use of foodsFood additives

Pharmaceutical chemistryDiscovery, testing, synthesis, commercial development of chemicals for medicine

Nuclear chemistryProduction and use of radioisotopes in medicine and industryStudying fundamental nature of nuclear reactions

Forensic chemistryCollection of evidence for use in lawIdentifying and tracing origins of substances found at crime scenes

Analytical chemistryDetermination of what substances are present in samples and how much is present

Physical chemistryStudy and measurement of physical aspects of compounds and reactions (rates, energy, structures, nature of bonding)

Organic chemistryStudy of compounds of carbonUsually associated with living matter

Inorganic chemistryStudy of compounds that are not organic, non-carbon-predominantMetals, extraction, reactions and compounds

Professor Kazacos invented the Vanadium battery. This uses the principle of oxidation and reduction reactions (electron transfer) to produce electricity from a battery. Her battery is rechargeable and uses different oxidation states of vanadium to produce the electron flow. The research involved testing many different combinations of electrodes and electrolyte solutions of vanadium with different oxidation states to find effective reactions combinations.

2. Chemical processes in industry require monitoring and management to maximise productionStudents Learn to: identify and describe the industrial uses of ammoniaFertilisers (sulfate of ammonium, ammonium nitrate and urea) NH3 is reacted with H2SO4 to form (NH4)2SO4 and with HNO3 to form NH4NO3HNO3 (used in explosives such as NH4NO3, TNT trinitrotoluene and nitroglycerine)Fibres such as plastics such as rayon, nylon and acrylicsHousehold cleaners NH4OH destroys bacteria, used in cleaning productsPharmaceuticals NH4OH is used to kill bacteria antiseptic soap and mouthwashes identify that ammonia can be synthesised from its component gases, nitrogen and hydrogen describe that synthesis of ammonia occurs as a reversible reaction that will reach equilibrium identify the reaction of hydrogen with nitrogen as exothermicN2(g) + 3H2(g) 2 NH3(g) -92kJThis reaction is reversible and will reach equilibrium in a closed system. The reaction is slow, exothermic and the equilibrium naturally lies to the left. explain why the rate of reaction is increased by higher temperaturesA rise in temperature will increase the particle movement in the substance, this increases the chance and force of collision of the particles, increasing the amount of successful collisions that exceed the activation energy. Therefore, the reaction rate is increased for both the forward and reverse reactions. explain why the yield of product in the Haber process is reduced at higher temperatures using Le Chateliers principleLe Chateliers principle states that if a system at equilibrium is disturbed, the system will adjust so as to minimise the disturbance.The Haber process is exothermic. If heat is added to the reaction, according to Le Chateliers principle, to minimise the effect, the equilibrium will move to the left to favour more reactants and decreases the product. explain why the Haber process is based on a delicate balancing act involving reaction energy, reaction rate and equilibriumThe rate of reaction must be increased as naturally the Haber process takes too long and produces too little yield. To speed up the reaction, a moderate amount of heat must be added to increase particle movement, increasing the rate of successful collisions. The reaction naturally lies to the left, so conditions must be altered so the equilibrium lies to the right, producing more yield. Adding heat to speed up the reaction rate will end up favouring the equilibrium to the left as the reaction is exothermic, which is undesired. Therefore, a compromise must be reached to produce most yield. The reaction is carried out between 450oC and 500oC. This allows the rate of reaction to increase. The removal of the NH3 and increasing the pressure will cause the equilibrium to lie to the right. explain that the use of a catalyst will lower the reaction temperature required and identify the catalyst(s) used in the Haber processA catalyst speeds up the rate of reaction by lowering the activation energy needed for a reaction to proceed without participating in the reaction. Because the activation energy is lower, not as much heat energy is required for the reaction to proceed.The catalyst used in the Haber process is magnetite (Fe3O4) with its surface layer reduced to free iron (Iron or iron oxide). analyse the impact of increased pressure on the system involved in the Haber processThe Haber process is the reaction between nitrogen and hydrogen to produce ammonia. This is an exothermic, reversible reaction where the equilibrium lies to the left.N2(g) + 3H2(g) 2 NH3(g) +92kJAccording to Le Chateliers principle, if the pressure on the system is increased, the reaction will proceed so that the pressure is reduced. That is, the side with the least number of gaseous moles.In the case of the Haber process, the RHS has less gaseous moles, so when the pressure is increased, the equilibrium will move to the right favouring the production of NH3. explain why monitoring of the reaction vessel used in the Haber process is crucial and discuss the monitoring requiredMonitoring of the vessel is crucial to ensure maximum yield (usually about 30%) for safety, oxygen mixing with hydrogen sould lead to an explosion and that no pollution occurs. Monitoring required: ratio of gases fed in N2:H2 = 1:3 purity of gases any oxygen present would cause explosion temperature and pressure must be maintained to ensure maximum yield the performance of the catalyst no gases are escaping but the H2 and N2 were returned to the reaction vessel and NH3 was removed disposal of wastesNote: NH3 is removed by cooling the reaction mixtures. This is possible because N2 and H2 are non-polar and have weak dispersion forces whereas NH3 is polar and forms H-bonds. As a result, the NH3 has a higher BP. When these gases are cooled, NH3 will condense first.Students: gather 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 historyGermany was reliant on saltpetre (sodium nitrate) from Chile for the production of bombs and crops using industrial ammonium for fertiliser and nitrates produced by it for explosives. This was transported by ship. Need for ammonia bad increased due to the increase in population need for more food, great use of land for cropping. The war also demanded more bombs. The British had planned to block Germanys supply of saltpetre in the sea.The Haber process gave Germany a distinct advantage in the war. This increased the length of the war and added greatly to the death toll. The Allies found not only did Germany no longer need to import saltpetre but they did at a greater expense.Fritz Haber produced ammonia in 1908 but in 1914, Carl Bosch successfully converted it into an industrial process.

3. Manufactured products, including food, drugs and household chemicals, are analysed to determine or ensure their chemical compositionStudents learn to: deduce the ions present in a sample from the results of tests describe 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 elementsAtomic Absorption Spectrum (AAS) allows quantitative analysis of many elements especially metals extremely sensitive can detect ppm can detect presence of more than one element in the sampleHow It worksAAS depends on the fact that eletrons exist in particular energy levels. An electron can move from one energy level to a higher one by absorbing electromagnetic radiation of a particular frequency. If electron falls to a lower energy level, it will emit radiation of particular frequency. Each element absorbs and emits radiation at particular frequencies. It is then possible to analyse a sample with more than 1 element.A sample of solution is sprayed into a flame to create a vapour of atoms. At the same time a light beam is passing through the flame. The light is at the wavelength known to be absorbed by that element. Atoms of the element absorb some of this light which is analysed by a detection system, which calculates and displays the absorbance. By comparing it to the absorption of standard solutions the concentration can be determined. This is possible because the absorbance is proportional to concentration.A standard is made by spraying a range of standard solutions of known concentration containing the element. The light absorbed by these is plotted against the concentration of the solutions and a calibration curve is obtained. The unknown solution is then tested and the absorption recorded. The concentration can then be read from the calibrated graph. New standards are made each time a test is done.Trace elements elements in very small amountsStudents: perform first-hand investigations to carry out a range of tests, including flame tests, to identify the following ions: phosphate: Ag+ ion, yellow ppt; Ba2+ ion, white ppt sulfate: Ba2+, white ppt carbonate: HNO3, CO2 bubbles chloride: Ag+ ion, white ppt barium: Light Green flame, H2SO4 white ppt (BaSO4) calcium: Orange flame, NaF white ppt lead: NO Flame test (toxic), Cl- white ppt (PbCl2); NH3 white ppt (Pb(OH)2), KI Yellow ppt copper: Green flame, OH- blue ppt (Cu(OH)2) iron: No reaction flame, Fe(OH)2 green ppt, Fe(OH)3 brown pptAnionFormulaTest

CarbonateCO32-Add HNO3, CO2 Bubbles will form

SulfateSO42-Add Ba2+, white ppt forms

ChlorideCl-Add Ag+, white ppt forms

PhosphatePO43-Add Ag+, yellow ppt formsAdd Ba2+. White ppt forms

CationFormulaFlame ColourPrecipitation Test

Lead (II)Pb2+N/A(Toxic vapour)Cl- ion, white ppt (PbCl2)NH3, white ppt (Pb(OH)2)KI, yellow ppt

BariumBa2+Light GreenH2SO4, white ppt (BaSO4)

CalciumCa2+OrangeNaF, white ppt

Copper (II)Cu2+GreenOH-, blue ppt (Cu(OH)2)

Iron (II)Fe2+No ReactionOH-, green ppt (Fe(OH)2)

Iron (III)Fe3+No ReactionOH-, brown ppt (Fe(OH)3)

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 societyHealth EffectsLead is a toxic heavy metal. It interferes with the enzymes in the body, inhibits the synthesis of haemoglobin and interferes with energy production by cellular mitochondria. Long-term overexposure can cause anaemia, damage to nervous system, kidney disease and decreased fertility. Only 2mg of lead can be excreted by the body per day. Excess lead accumulates in the bones and teeth where it replaces natural calcium.EvidenceLead-based paints have proved to be a problem in young children, who crawl on the ground and inhale and/or ingest lead paint dust or flakes. As AAS allowed an accurate test of childrens blood lead levels, which showed an alarmingly high concentration of lead. This led to the legislation being changed and banning lead-based paints.AAS also showed people who lived near main roads had a higher lead concentration in their blood as people who lived away from main roads, this led to the banning of lead in petrol.Lead contaminated can also be from lead pipes, solder, car batteries, industrial emissions, smelting lead ores and mining. The recommended target for blood lead level is O3 (g)H = -106 kJ/molFree radicals can react with ozone, UV can decompose ozone by absorption.O.(g) + O3 (g) -> 2O2 (g)H = -390kJ/molO3(g) + UV -> O.(g) + O2 (g)These reactions are exothermic and release heat to the stratosphere.There is a balance between the formation and depletion of ozone leading to a steady state in the upper atmosphere.Ozone in the lower atmosphere (in troposphere) is formed when sunlight reacts with NO2.NO2(g) + sunlight -> NO(g) + O.(g)O2 (g) + O.(g) -> O3 (g)The formation of ozone occurs when the UV levels and NO2 levels are at their highest. (midday etc). it is a pollutant because it oxidises organic tissues, including plant tissues, and disrupts normal biochemical reactions in the body. It irritates the eyes and causes breathing difficulties. It also reacts with plastics and rubber. describe the formation of a coordinate covalent bondA coordinate covalent bond is one where both of the shared electrons came from the one atom. Once formed, this bond is indistinguishable from all other covalent bonds.

Ozone is a bent molecule. demonstrate the formation of coordinate covalent bonds using Lewis electron dot structures

compare the properties of the oxygen allotropes O2 and O3 and account for them on the basis of molecular structure and bonding compare the properties of the gaseous forms of oxygen and the oxygen free radicalAllotropes different structural form of an element in the same state.PropertyO2 (Oxygen Gas)O3 (ozone)O. (Free radical)Explanation

Colour and OdourColourlessOdourlessPale blue gasSharp, pungent odour (toxic)Toxic, reacts w/ organic molecules in living cells

MpBpMp is -218oCBp is -183oCMp is -193oCBp is -111oCBP of O2 is lower than O3 b/c smaller molecular mass, requires less energy to break. Inter-molecular forces b/w O3 stronger than O2

Solubility in waterSlightly solubleMore soluble than O2More soluble than O3O2 non-polar, water poler, not soluble. O3 bent, polar, more soluble. Radical more reactive

Reactivity

Oxidation abilityModerately reactive, decomposed by high energy UV

Less powerful oxidantHighly reactive, unstable, decomposed by medium UV

More powerful oxidant, react w/ alkeneExist briefly, reacts immediately, highly reactive w/ living cells2O. -> O2 (g)O3 unstable, easily decomposes to O2. O2 is stable (complete valence shell) Free radical, no full valence shell, most reactive

Structure and bondingDiatomic molecule 2 O atoms held together by covalent bond3 oxygen atoms held together w/ one double bond and 1 single coordinate covalent bondEast radical contains two unpaired valence electronsBonding: O3 polar b/c donation of e- from centre leaves it little positive. Usually as O atoms have same electronegativity, e- are evenly shared. O2 is non-polar, both dispersion, O3 stronger

ShapeO=OLinearO=O OBent & polar

Free radicals A neutral species (no charge) that has one or more unpaired electron. It can be formed by splitting a molecule into two neutral fragments. It is very reactise as presence of unpaired electron and incomplete valence shell

identify the origins of chlorofluorocarbons (CFCs) and halons in the atmosphereCFCs Chlorofluorocarbons compounds containing chlorine, fluorine and carbon ONLY. They have no hydrogen.OriginsOriginally as a refrigerant as it was unreactive, odourless, non-flammable and non-toxic. Laster were used as propellant in aerosol cans and foaming agents in polystyrene production. They were used to clean circuit boards and as a refrigerant in air conditioning systems.Eg. trichlorofluoromethane, dichlorodifluoromethane, ,1,1,2-trichloro-1,2,2,-trifluoroethane

Halons compounds containing carbon, bromine and other halogens. There is no hydrogen. This is a problem as bromine is more reactive than chlorine and have a greater potential to deplete ozone. They are not used as widely as CFCs.OriginsFire extinguishers used on electrical appliances.Eg. bromochlorodifluoromethaneHalons are fully halogenated chemicals that have long lifetimes in the atmosphere. They are broken down in the stratosphere releasing reactive bromine. Bromine is estimated to be responsible for 25% of ozone destruction over Antarctica and 50% over Arctic. The ozone depleting potential of halons is 10x greater than CFCs. Halons are very aggressive ozone depleting chemicals. Australia stopped importing halons at the end of 1992. Halons entered the atmosphere when fire extinguisher were used or tested. identify and name examples of isomers (excluding geometrical and optical) of haloalkanes up to eight carbon atomsIsomers compounds that have the same molecular formula but different structural formula.Naming Haloalkanes1. Identify the halogen functional group, naming with prefixes in front of the name of the alkane in alphabetical order: Bromo, chloro, fluoro, iodo, If there are more than one of halogen, use prefix di, tri, tetra etc2. Count no. of carbons in the longest unbranched carbon chain containing the halogens and use the appropriate stem name. Attach ane.3. If there are branched chains, count no. of carbons, identify appropriate stems and attach yl. If there are more than one, then use di, tri, tetra etc. 4. Halogen and side group names are in front of main stem name, in alphabetical order ignoring di, tri prefixes5. Number the carbon chain from the side that allows lowest numbers before the halogens, when there are more than one halogen, place the lowest number in front of the halogen that will be named first discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problemsCFCs are inert. They are not decomposed by sunlight at low altitudes. They are insoluble in water and so are not washed away by rain. They diffuse slowly into the stratosphere. In the stratosphere, they absorb short UV radiation to form two free radicals:CCl3F + UV -> Cl. + .CCl2FCl. Is very reactive, reacts with O3. ClO then reacts with O. to form O2 and Cl.. Cl. is then a catalyst to the chain reaction until Cl. reacts with methane or NO2.Cl.(g) + O3(g) -> ClO.(g) + O2(g)ClO.(g) + O.(g) -> O2 (g) + Cl.(g)The overall reaction: O.(g) + O3 (g) -> 2O2 (g)Termination:CH4 (g) + Cl.(g) -> CH3. + HClNO2 + ClO.(g) -> ClONO2This results in the depletion of ozone which means more radiation reaches the earths surface. (cancer, cataracts etc) CFCs are inert, they last up to 150 years in the stratosphere.Steps to alleviate problemThe problem with the ozone layer was first observed in the 1970s. Ban the use of CFC and Halons Montreal Protocol international treaty (1987) observed by 27 countriesAlternatives used HCFCs and HFCsAssistance to developing countries to phase out CFCs analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and explain how this information was obtained

The information shows that the ozone levels change seasonally.It has been observed that ozone level have decreased in the stratosphere especially over the Antarctic. In 1970s it was discovered that CFCs were depleting the ozone layer. In the 1980s the ozone less worsened, 1985 it had declined about 30% and more recently 50%. The greatest decline is during spring. The winter is extremely cold and no sunlight is present at the Antarctic but with the coming of spring, UV light is present and ozone is destroyed.

MeasurementMeasurements of the total amount of ozone in a column of atmosphere have been recorded since 1957.The amount of ozone is measured by spectrophotometers on the ground in weather balloons or on satellites. This gives a reading of the total ozone in the atmosphere per unit area in Dobson Units. (One Dobson unit is the amount ozone that corresponds to a 00.01mm thick of pure ozone at atmospheric pressure. The normal amount of ozone is 300DU.)In the past satellites were used to carry a device called a total ozone mapping spectrophotometer (TOMS), which proved very efficient in recording changes in ozone levels. The ozone column is determined by differential absorption of solar radiation at two adjacent UV wavelengths. (measures backscattering)In 2004 NASA measured the amount of ozone daily using a satellite spectrophotometer called Ozone Monitoring Instrument (OMI) located on Aura satellite. It measures backscattering more accurately using a greater range of wavelengths.In 2012 NASA launched new satellite NNP with Ozone Mapper Profile Suite (OMPS) which measure vertical distribution of ozone in the stratosphere as well as ozone in lower strosphere and troposphere with high vertical resolution.Students: present 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 gather, process and present information from secondary sources including simulations, molecular model kits or pictorial representations to model isomers of haloalkanes present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCsHCFCs (hydrochlorofluorocarbons) were the first alternative because H-C bond are decomposed in the troposphere to a significant extent. Only small portions of them reach the stratosphere. While this means they destroy less ozone, it is still significant. HCFCs reduce ozone depletion when compared to CFCs and is hence an effective first alternative to CFCs. However, they still cause some degree of ozone destruction, so better alternatives must be found.They are replaced by HFCs (hydrofluorocarbons) which contain no chlorine and are decomposed in the troposphere. They dont destroy zone. They are more expensive than CFCs and not as effective. These dont deplete the ozone, and is hence more effective than HCFCs, however, their practical use is lower, it is effective in terms of protecting the ozone but not effective in practical use.There has been a significant drop in production of CFCs but we cant remove CFCs already in the stratosphere. So come measures are needed to reduce the effects of problems caused by CFCs such as high UV radiation. These include: people using new sunscreens, as advised by Cancer Council the use of UV stabilizers in polymers that are exposed to sunlight to reduce breakdown by UV

5. Human activity also impacts on waterways. Chemical monitoring and management assists in providing safe water for human use and to protect the habitats of other organisms identify that water quality can be determined by considering: concentrations of common ions total dissolved solids Hardness Turbidity Acidity dissolved oxygen biochemical oxygen demand

identify factors that affect the concentrations of a range of ions in solution in natural bodies of water such as rivers and oceans Frequency of rain floods and droughts, more or less rain will change concentration of solute Water temperature more solute dissolves if water warmer, increase conc Evaporation rate more evaporation, increase concentration Soil type mineral content of nearby soils Pollution faeces, fertilisers, nitrates and phosphates from agricultural run-off Land use: Forestry increase soil run off, branches, more leaching Farming pesticides, fertiliser Mining heavy metals Landfill heavy metals, chemical leach, bacteria Untreated sewage bacteria describe and assess the effectiveness of methods used to purify and sanitise mass water suppliesProcessWhat is removedPhysical/Chemical processAssess

Screening Larger, undissolved solidsEg. Wood, plasticPhysical ProcessSieves are used to screen out any large insoluble matterLow cost, no added chemicalsRemoves most solids but not allEffective for large solids

FlocculationFine suspended particlesEg. Decomposing organic matter, fine sedimentChemical ProcessAl2(SO4)3is added to water with Ca(OH)2. It forms Al(OH)3 precipitate, sticky and gelatinous. The suspended solids stick to the Al(OH)3, absorption. The Al(OH)3 then clump together, heavier particles, forming lumps called floccs. The heavy particles settle out as sludge at the bottomVery successful process to reduce turbidity. Removes the majority of unwanted particles easily. Helps the filtration process speed up and use less energy. Doesnt remove bacteria.

Sand FiltrationSmaller solid particles and floccsPhysical processFilters are often sand, gravel and coalNecessary step after flocculation. Doesnt remove very fine solids.Does not remove bacteria

ChlorinationBacteria and microorganismChemical ProcessChlorine gas added to water:Cl2(g) + H2O(l) -> HOCl(aq) + H+ + Cl-HOCl kills the bacteria, bleach coloured compounds and remove tastes and odours in the water. Effective - most harmful micro-organisms removed, Giardia Cyrptospiridium. Chlorine remains in water, keeps disinfecting it.

pH AdjustmentNothing is removedChemical ProcessLime, CO2are added to adjust the pH to make it more suitable for household useThis step is successful as it also helps to improve the safety of the water.

describe the design and composition of microscopic membrane filters and explain how they purify contaminated waterA membrane filter is a thin film of a synthetic polymer through which water is filtered. Its made of poly propylene, polytetrafluoroethylene and polysulphone. There are pores of fairly uniform size. The size of the hole determines what remains as the residue.They can be classified as microfiltration 0.1 micron, ultrafiltration 0.01 micron, nanofiltration 0.001 micron and can be coated to remove heavy metal ions, or reverse osmosis membranes depending on the size of the pore.Microfiltration removes bacteria, protozoan, large viruses, pollen and silt. The extremely fine holes allow water but not large organic molecules or microorganisms to pass through. The water is pumped across the surface over the membrane rather than through it. This reduces blockages, the water then passes through the membrane and into the core. The filters need to be back flushed for cleaning.

Students: perform first-hand investigations to use qualitative and quantitative tests to analyse and compare the quality of water samples gather, process and present information on the range and chemistry of the tests used to: identify heavy metal pollution of waterHeavy metals refer to metals with a high atomic mass. They are naturally present in soil and water at low concentrations. Some of these metals are essential to biological life - trace elements. Pollution caused the levels of heavy metal in the environment to rise and this causes various health issues for organisms (including humans).Human activities cause heavy metals such as Lead and Mercury, which are used in industries, to enter the environment into waters and soil.Lead is poisonous to organisms. It damages the nervous system, kidney, cause anaemia and death. A flame test cannot be conducted (toxic vapour). Adding KI will form a yellow ppte. Mercury is also a poisonous heavy metal. It can cause memory loss and insomnia. If exposed to high levels, it can produce hallucinations, damage the brain and birth. Add KI, will form a red ppte. Quantitative tests for heavy metals include volumetric and gravimetric analysis, colourimetry, chromatography ad spectroscopy (AAS Atomic Absorption Spectroscopy) and mass spectroscopy. monitor possible eutrophication of waterwaysThe process of eutrophication involves the increase in nutrient content of a body of water resulting in excessive growth of plants, when they die, cause oxygen depletion during the decay process.The offending nutrients are most likely to be nitrates (from fertilizers and untreated sewage) and phosphates (from fertiliser run-off and/or from detergents).Eutrophication can be detected by measuring the dissolved oxygen (low dissolved oxygen would indicate eutrophication) and nutrients such as nitrates and phosphates.Phosphates and nitrates are measured using colourimetric tests. Nitrates and phosphates are reacted with standard reagents to form coloured compounds. The depth of colour is the measured and converted to concentration unites using a calibration curve. gather, process and present information on the features of the local town water supply in terms of: catchment areaA catchment is an area where water is collected by the natural landscape. In a catchment, all rain and run-off water eventually flows to a creek, river, lake or ocean. Catchment areas determined by geographical features of the land. Boundary is defined by a ridge where water flows in the opposite direction away from the catchment basin. possible sources of contamination in this catchmentContaminateSourceTreatment

Twigs, branchesForestryScreening

Suspended solidsEutrophicationReverse osmosis

Fertilisers pesticidesAgricultural run-offReverse Osmosis

BacteriasewageChlorination

chemical tests available to determine levels and types of contaminantsTurbidity, pH, dissolved oxygen, temperature and conductivity are all carried out in the field with a Data Logger.Chemical tests in the lab can be done to determine presence of elements and ions, including precipitation, flame test, ASS, colourimetry, chromatography. physical and chemical processes used to purify waterScreening, Flocculation, Filtration, Chlorination, pH adjustment chemical additives in the water and the reasons for the presence of these additivesFluoride is added to drinking water after disinfection to reduce dental problems. It is added in the form of Na2SiF6, H2SiF6 and NaF. This process is supported by most health organisations. Fluoride interacts with tooth enamel to make is stronger and more resistant, especially to low pHs. It can also remineralise some small defects in the tooth before they become cavities. It can also kill some bacteria.Hard water is unsuitable for household use. Soap doesnt lather in hard water and boiling hard water in kettles ruins the kettle. Sodium carbonate decahydrate (Na2CO310H20) can be added to water to soften it. It is able to make the Ca2+ ions precipitate out in the form of CaCO3 which is insoluble in water. However, it doesnt remove other metal ions in the water.

Dirty, contaminated water

Leaves, twigs and rubbish removedScreening and Filtration

Suspended solids, iron precipitate, some bacteria removedFlocculation

Remaining solids removedFiltration

Bacteria and viruses removedChlorination

pH Adjustment

Water for Household use

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