TOPIC THREE

Topic Three

Chemical Monitoring and Management

Contextual Outline

The 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.

Burhan Gemikonakli is a analytical chemist at Qenos, a major Australian Chemical manufacturing company that makes ethylene from ethane and then polymerises it to polyethylene.His role is to

Monitor the quality of the ethylene produced by the plant to ensure that it meets the requirement for the next stage of manufacture

Especially determining the nature and amount of impurities present Monitoring waste water from the plant to ensure it meets environmental requirements before it is discharged

Collaborating with process engineers to adjust operating conditions in order to optimise product yield

The branch of chemistry used is mainly analytical chemistry which is concerned with determining the nature and amount of substances present in each material.

The technique used is gas chromatography. It uses the chemical principles of adsorption and solubility.

A liquid or gaseous mixture is vaporised into a stream of helium that flows over a stationary phase. This is coated within a long thin glass capillary tube. The substances pass through at different rates due to the solubility/adsorption and in accordance, a device at the end of the column detects each substance as it passes out and measures it quantitatively

Chemistry is such a broad discipline that chemists specialise in particular branches. Solving complex problems requires input from many chemists with different specialities. It is essential that chemists work collaboratively and exchange their different view points as they collect and analyse data.

Environmental chemistry concerned with determining how substances interact in the environment with monitoring concentrations of substances, particularly pollutants in air, water and soil

Polymer chemistry a branch involved with developing new polymers with particular properties, working on how polymerisation occurs and working on its efficiency while studying the properties of polymers.

May also focus on creating new polymers with other properties for other uses

Aims to improve the structure and alter properties to create new substances

Food chemistry looks at chemical aspects of the production, preservation and use of foods and chemicals added to food

Nuclear chemistry focuses on the production and uses of radioisotopes in medicine and industry as well as studying the fundamental nature of nuclear reactions e.g. fusion/fission.

Complete combustion this is combustion with an adequate supply of oxygen forming water and carbon dioxideCH4(g) + 2O2(g) ( CO2 (g) + 2H2O(l)Incomplete combustion this is combustion without an adequate supply of oxygen forming water and/or carbon monoxide and carbon (soot)

2CH4(g) + 3O2(g) ( 2CO (g) + 4H2O(l)CH4(g) + O2(g) ( C (s) + 2H2O(l)Carbon monoxide is toxic gas as it irritates the breathing of humans

Carbon soot is carcinogenic

It is important to monitor the conditions in a reaction such as combustion in order to ensure

Minimising the production of CO or C as they are harmful substances

It is used for Fertilisers

Fibres and plastics

Nitric acid

Household cleaners

Detergents

It is widely used as a fertiliser to grow crops for the growing population. Ammonia is reacted with sulfuric acid or nitric acid to form ammonium sulfate or ammonium nitrates which is used as fertilisers.

The raw material for ammonia productions are nitrogen gas and hydrogen gas

Sources

Nitrogen can be obtained directly from the atmosphere via fractional distillation

Hydrogen can be obtained several ways depending on the available resources

Electrolysis of water 2H2O(l) ( 2H2(g) + O2(g) React natural gas (e.g. methane) with steam

CH4(g) + H2O(g) ( 3H2(g) + CO(g) CO(g) + H2O(g) ( H2(g) + CO2(g) The CO2 can further be used to be carbonated drinks

Ammonia is prepared by the reversible reaction called the Haber process between hydrogen and nitrogen gas. The forward reaction is exothermic

N2(g) + 3H2(g) 2NH3 (g) H = - 96kj/mol

A chemical reaction involves the collision of particles. At higher temperatures, the particles gain more kinetic energy and move more quickly. This increases the chance of collisions and thus increases both the forward and backward rate of reaction.

N2(g) + 3H2(g) 2NH3 (g) H = - 96kj/mol

If the temperature is increased, the equilibrium will favour the endothermic reaction and minimise the change by absorbing the heat. Thus in the Haber process, at higher temperatures, the equilibrium will shift to the left, decreasing the yield of the product

Pressure:

At high pressure, the rate of reaction will increase as the particles have more chance of collisions

At high pressure, the yield of ammonia is increased as it the side with less gaseous molecules and by Le Chateliers principle, the system will shift to this side to minimise the high pressure changes

Impact of pressure High pressure systems is very costly and there is a risk of an explosion, but does increase both the rate and yield. Thus a compromise of 250 350 atm is used

Temperature

At high temperature, there is a high rate of reaction, but low yield

At low temperature, there will be an increase in yield, but very slowly

A compromise for both temperature and pressure is required for a decent yield and a reasonable rate of reaction. This is a temperature around 400 500oC

The use of a catalyst lowers the activation energy for the reaction. This will increase the rate of reaction at lower temperatures. The hydrogen and nitrogen molecules are adsorbed onto the surface of the catalyst where they react to form ammoniaThe catalyst is usually a mixture of iron and iron oxide or magnetite Fe3O4

The condition of the reaction vessel must be monitored in order to ensure it is a safe and optimised process. The conditions which are regularly monitored are:

Temperature this is compromised between the rate of reaction and yield of 400 to 500oC. This must be monitored to keep them in this range for optimum conversion of reactants to products or else it will be too inefficient and costly to stabilise. Excess temperature may damage the catalyst

Pressure This is kept in a range of 250 350 atm. Too high pressure may cause an explosion

Composition of incoming gas must also be monitored

Ensure ratio of hydrogen gas to nitrogen gas is 3:1 which their stiochiometrical ratio is. Excess of one reactant will slow down the reaction

Ensure there is no oxygen as it can cause an explosion

Ensure CO and sulfur containing species are removed as they poison the catalyst

Ensure there is no unreactive gases which may lower the efficiency

Also the ammonia is liquefied out so it shifts the equilibrium to the right, thus increasing the yield

German scientist Fritz Haber first developed the method of synthesising ammonia from its elements in which Bosch turned it into an industrial process. The main source of ammonia before then was from imported from Chile, however this source was cut off by the British naval blockade.

The production of ammonia was important for both the production of fertilisers and explosives. Fertilisers were needed to grow food crops in order to solve the diminishing food supplies due to the war to feed the population. Hence the Haber process was significant at that time as it prolonged the length of the war and illustrates the impact of the development of science.

Identifying ions refer to sheets + text book

The main ways are

Precipitation reactions

Flame tests (only for cations)

Some metallic atoms display a characteristic colour when subjected to a flame

When these atoms are subjected to an external energy supply, the electrons gain energy and jump to the outer empty levels. When these electrons fall back down to their ground state, they release this energy in the form of photons or light at a particular wavelength. The wavelengths in the visible region will produce a set of distinctive colours known as the emission spectrum. The wavelength of light emitted is unique to that particular element

Ba2+ - greenCa2+ - redCu2+ - blue/green

Phosphate this often occurs in natural waterways at low concentrations, but if high enough can cause eutrophication. This rapid algal bloom can completely cover the surface of the lake or river, killing most marine life forms. It also increases the BOD and eventually uses up all the DO in the water. It suppresses photosynthetic processes due to the blockage of sunlight and also creates cyanobacteria. When it uses up all the phosphate, it dies and has further detrimental effects on the waterway. Thus the monitoring of phosphate is essential to prevent any harm

Lead this is a poison, it retards intellectual development and causes brain damage, leading to neurological disorders. It was widely used in petrol and hence released into the atmosphere and waterways. It was also a constituent of house paints which can release lead into the soil and waterways. This is extremely dangerous for both the marine organisms and the humans whom access this waterway. Thus it is extremely important the levels of lead are monitored in a waterway.

The use of AAS

AAS allows us to measure the small concentrations of cations in a sample, it is highly accurate and can go up to the ppm/ppb ranges

From the emission spectrum, we know the exact wavelengths absorbed or released by a particular element (can be found by using AES). Hence if the element is supplied with those wavelengths, the electrons of the atoms will absorb those wavelengths and undergo transition

In AAS, a special light source producing specific wavelengths known to be absorbed by the element tested is used. The light is passed through a flame containing a vapourised sample of the test element

A filter is used to select a particular frequency and a detector is used to measure the transmitted intensity after being passed through the atom. From a comparison between the transmitted intensity and the original intensity, a percentage of absorption can be determined. From a standard calibration graph, the concentration can be determined.

The Lamp: a hollow cathode lamp of the element being measured. The lamp generates wavelengths of light specific to the element being analysed.

The Flame (Atomiser): the solution is sprayed into a flame or graphite furnace. At the high temperatures of the flame/furnace, the element is reduced to its atomic state.

As light passes through the atomised sample some of the light is absorbed by the hot atoms. The remaining light passes through a monochromators/filter to select only the wavelength band to be measured.

The light beam then passes to a photomultiplier, which detects the intensity of the light. The difference in intensity from the original value (no sample) to the final value (with sample) is directly proportional to the concentration of the element in the atomised sample.AAS is used in measuring the concentration of trace elements. These are elements required by living organises in very small amounts to help enzymes function. Common trace elements required are Zn, Co, CU, Ni and Mn. AAS can provide crucial evidence when dealing with soil or pasture deficiencies. It can identify the particular trace element that needs to be added in order to improve animal health and efficient agriculture which is of tremendous importance as it provides food sources where previously no crops would grow. South Western Australia animal health could not be maintained on seemingly good pastureland. AAS showed cobalt deficiencies in the soil and the pasture

Parts of Victoria could not support crops until molybdenum deficiencies were detected by AAS and rectified

The use of AAS can lead to improved environmental monitoring which has obvious positive benefits for society and the environment. AAS can detect very small concentrations of metals, especially heavy metals such as Pb, Cd, Hg, in the environment before those concentrations are high enough to cause significant damage to the environment and those who access it. AAS is an automated procedure and easy to use in providing quick and accurate results to monitor and detect routinely harmful metals in food, effluent, waterways and the environmentLimitations

Lacking portability

AAS data on heavy metals is limited by the different sensitivity or detection limits for each metal

Can only be used for cationsEvaluation hence the use of AAS in pollution is very effective.

Aim : to measure the sulfate of lawn fertiliser

1g of fertiliser was weighed ground in a mortar and pestle. This was then dissolved in approximately 250ml HCl with staring

This was heated gently to near boiling and excess barium sulfate was added while stiring

The mixture was then cooled and filtered out

The mass was measured

The method is valid since BaSO4 has low solubility

Errors:

Passage of barium sulfate through the filter as the crystals are very small

The precipitate may bad adhered to the walls of the beaker while being transferred

Incomplete drying of precipitation which still contains water, gives inaccurate mass measurement

Solutions

Use a desiccator to dry

Use a vacuum pump for filtration or use a sand/membrane filter

At atmosphere is a blanket of gases above the earths surface. The gases are held together by gravitational forces. It provides the gases essential for many life forms.

Layers of the atmosphere Troposphere 0 15km

Closest to the earths surface

Provides gases essential for many life forms e.g. oxygen, CO2 and nitrogen

75% of the mass of the atmosphere is found here

Stratosphere 15 50km

Contains the ozone layer , its concentration varies between 2 to 8 ppm

Mesosphere 50 85km

Thermosphere 500km

Exosphere 1000km

Composition

Gases

Concentration (%v/v)

Nitrogen

78.1Oxygen

20.9Argon

0.93

Carbon dioxide

350ppm

Carbon monoxide cars exhaust, Cigarettes, forest and farm fires

Oxides of nitrogen combustion from vehicles and power stations

Hydrocarbons unburnt exhaust, gases from vehicles and factories

Sulfur dioxide combustion of impurities in coal, metal extraction

Ozone high voltage discharges, photochemical smog

Ozone is an allotrope of oxygen. It is slightly polar due to its bent shape In the troposphere, ozone is a pollutant. It is toxic for all life forms as it causing breathing difficulties, aggravates respiratory problems and produces headaches and premature fatigue. This is because ozone is a powerful oxidising agent; hence it can cause oxidation of tissue in the living body. This disrupts normal biochemical reactions occurring in the body.

Ozone is formed in this layer when sunlight is very intense and the concentrations of No2 are well above clean air levels

NO2(g) + sunlight ( NO(g) + O(g)O(g) + O2(g) ( O3(g)But NO can also destroy ozone NO(g) + O3(g) ( NO2(g) + O2(g)The formation of ozone depends on the ratio of the concentration of NO2 to NO. When the ratio is about 0.3, the ozone is destroyed as quickly as it is formed. However if the ratio is too high, ozone is formed at a greater rate than it is produced, then there may be a build up of ozone concentration (ratio of 3 : 1)

In the stratosphere, it acts as a radiation shield by absorbing all the harmful UV rays which may damage living tissue. It absorbs most UV-B and UV C.

(this type of formation is only possible in this layer)

O2(g) + UV radiation --( 2O(g)O(g) + O2(g) ( O3(g) [exothermic reaction]

A coordinate covalent bond forms when one atom in a provides both electrons in the covalent bond. Once formed this coordinate bond is indistinguishable from other covalent bonds.

PropertyOxygenOzoneExplanation

Colour colourless gas

pale blue liquid colourless gas

distinct blue liquid

Boiling point-1830C-111oCOzone has a greater molecular mass than oxygen and is more polar, hence greater dispersion forces

StabilityVery stableEasily decomposes to O2

ReactivityLess reactiveMore reactive. It is a very strong oxidising agentDue to the weak co-ordinate covalent bond

Oxidising LowHighOzone is a powerful oxidising agent to its high tendency to receive electrons

Solubility in waterLess solubleMore solubleO3 is slightly polar due to its bent shape where as O2 is non-polar

Oxygen radical This is the oxygen atom in its ground state has 3 pairs of electrons in its valence shell. This is the most reactive due to the unpaired electrons

Formed by the splitting of a normal oxygen gas molecule by UV radiation

Oxygen gas very stableOzone:

Poisonous and powerful oxidant

Less reactive than the oxygen radical, but more reactive than hydrogen gas

CFCs

These are Halo alkanes with all hydrogen atoms replaced by chloro or fluoro functional groups

Since they were inert, non-toxic, and not soluble in water, they were the best replacement for ammonia as coolants in refrigerants

They were used in air conditioners and propellants such as aerosol

Halons Used in fire extinguishers

Isomers are molecules with the same molecular formula but have a different structural formula. The longer the chain, the more isomers possible.

Ozone depletion is a major issue as it results in more UV radiation reaching the earths surface.

This causes:

Increased incident of sunburns and skin cancers

Increased risk of eye cataracts

Increased risk of disease and illness

Increased plant growth

Increase damage to synthetic materials

It was found that CFCs and halons are the main factor that destroys the ozone layer in the stratosphere. CFCs are not destroyed at low altitudes by sunlight and oxygen as they are inert and insoluble, thus not removed by rain. Hence once released, CFCs remain in the troposphere for a very long period of time and slowly diffuse into the stratosphere.In the stratosphere CFCs break up by sunlight and form a reactive chlorine radical

CCl3F(g) + UV light ( Cl(g) + CCl2F(g)Cl(g) + O3(g) ( ClO(g) + O2(g)The free chlorine oxide radical can react with the oxygen present in the stratosphere to regenerate this chlorine atom

ClO(g) + O(g) ( Cl(g) + O2(g)As the Cl free radical is regenerated in this continual process (a chain reaction), each CL radical can destroy thousands of ozone molecules before being removed by other process such as chain carrier removers. Hence the use of CFCs is highly dangerous as it has high ozone depletion potential.

Steps taken to alleviate these problemsSince it is not possible to remove the CFCs from the atmosphere, the only way to rid the atmosphere of them is to cease any emissions of CFCs International agreements:

There have been several agreements in which nations have undertaken to phase out the use of CFCs and other ozone destroying compounds. The original one was the Montreal protocol but amended and steps accelerated by the one in Copenhagen

Stop using halons by the end of 1994

Case the use and manufacture of CFCs by 1996

Phase out HCFCs

Allow less developed countries some period of grace and financial assistance

This has proven to be effective as CFC production in developed countries have ceased and the atmospheric concentrations of CFCs have been reduced

CFC replacements

HCFCs- These compounds contain C=H bonds and are oxidised in the troposphere to form carbon dioxide, water and hydrogen halide molecules. Hence only a small portion reaches the stratosphere and their ozone depletion potential is less. However it is still significant and were only used as a temporary substitute for CFCs until better replacements found.

HCFs These compounds do not contain chlorine atoms, only hydrogen and fluorine atoms. Hence their ozone destroying capacity is close to zero and decomposes easily in the troposphere. However they are more expensive and less efficient than CFCs, but alleviates the problems to the ozone holeEvaluation

The steps taken to alleviate the problems associated with the use of CFCs have been extremely effective as current evidence suggests that the ozone hole is closing and ozone levels in the stratosphere is increasing. However it will take a long period of time before the problems associated are solved.

Measurements of the total amount of ozone in a column of atmosphere have been recorded since 1957. It was discovered that in the 1970s, CFCs were depleting the ozone layer. Observations around the world have shown that the ozone layer thickness is significantly thinner than in the previous years and being most depleted over the Antarctic during spring. Seasonal influences During winter, it is a period of continuously darkness and the stratosphere at this location is extremely cold. Under these conditions, certain solid particles catalyse a reaction between hydrogen chloride and chlorine nitrate HCl + ClONO2 ( Cl2 + HNO3 When sun comes in spring, the sunlight splits the chlorine molecule into two separate chlorine atoms and these process to destroy the ozone layer

Monitoring Stratospheric Ozone

Ground based instruments are UV spectrophotometers pointing vertically up at the atmosphere. They measure the intensity of light received at a wavelength at which ozone absorbs and then at wavelengths to either side of this one. A comparison of these gives a measure of the total ozone in the atmosphere per unit area of the earths surface at this location

Total Ozone mapping spectrophotometers These are onboard satellites and apply the same principle, but are able to provide for a much larger scale as they orbit the earth

Atmospheric instruments Huge helium balloons carry instruments such as the UV spectrophotometers and measure the concentrations of various substances at high altitudes

Concentration of Common ionsMost metal cations can be detected with AAS which is most practical as they are generally in very small concentrations. These need to be monitored as they can indicate water quality

TDSTotal Dissolved Solids are typically dissolved salts, generally reported in ppm. Healthy water should have a TDS of less than 100ppm. Any higher and the water is considered as contaminated with levels of greater than 1000ppm signifies very unhealthy water which has limited use.

It can be measured in two ways, evaporation or electrical conductivity

Evaporation The amount of TDS can be measured by evaporating a filtered sample of water to dryness and weighing the residue. The evaporation must be carried out slowly to prevelt loss by turbulent bubbling and spitting

Conductivity Nearly all solids dissolved are ionic salts. Therefore it this is commonly used as it is much quicker and can be done in the field

Water HardnessHard water is described as water that does not form a good lather with soap due to the presence of Ca and Mg ions, instead it forms a grey scum. Water with low concentrations of these ions is called soft water

Soap is sodium stearate C17H35COONa and is used to lower the surface tension so water can stick to oily particles which then can be removed. Instead with hard water the stearate ions precipitate with magnesium or calcium. Water hardness can be measured by titration with EDTASolutions to water hardness would be using a water softener where an ion exchange would occur. The calcium/magnesium ions were replaced with sodium with the disadvantaged that it needed to be replaced regularly. Another solution is to use synthetic detergents instead of soap.

Turbidity

Turbidity in water means cloudiness of lack of transparency due to suspended solids. It indicates the ability of water to support life as very turbid water systems will suppress photosynthetic activity, dangerous for animals inhabiting the water system and those accessing it. Sources include such as clay, silt, plankton, industrial waste and sewage

This can be qualitatively measured by using a turbidimetry tube with a secchi disc.

Acidity

The pH of aquatic systems are dependent upon the water source, geology and levels of biological activity. Freshwater bodies near limestone soils will be slightly alkaline. Pollution sources such as acid rain, exposure to sulfide ores can result in low pHs.

Dissolved Oxygen and Biochemical Oxygen demandOxygen has a very low solubility in water (healthy water is 9ppm at 20 degrees). However this small amount that is dissolved is of vital importance to fish and other aquatic life forms. If the water is depleted of dissolved oxygen, it can suffocate fish as well as causing stress to many aquatic organism.

DO is a good indicator of water quality. Sources of dissolved oxygen include photosynthesis of plants and surface water directly absorbing oxygen. If it falls below 5ppm, many aquatic species will die or fail to reproduce, making it eventually unfit for human consumption. The DO can be measured by using an electronic oxygen sensor for the winkler methodThe biochemical oxygen demand is a measure of the concentration of dissolved oxygen required for the complete breakdown of the organic matter in the water by aerobic bacteria. In order to measure this, firstly measure the DO on the first day, then put it in a sealed container without sunlight for 5 days. Measure the Do every day and compare, the difference between the first and last day is the BOD

The pathway, frequency and temperature of the water. Rain travelling into streams will dissolve ions in natural nutrients and decomposing minerals along the way. Rain that leeches deep in the earth contains more heavy metal ions due to the minerals present in the rocks and soils through which ground water passes through

The more frequent rain, the more possible ions

Higher temperatures will allow more ions to be dissolved in the run off

The presence of human practices

Agricultural practices such as the use of fertiliser and manure which contains anions such as phosphate, sulfate and nitrates

Land clearing, allows water to rapidly run across the land and into streams, increasing turbidity and facilities the dissolution of ions

Discharges of waste from industries and mines

Leeching from poorly designed rubbish tips and dumps

pH of rain

There are 6 basic steps : Aeration -> Flocculation -> Sedimentation -> Filtration -> Chlorination -> Fluoridation

1. Aeration The water is sprayed into the air to increase the concentration of DO

2. Flocculation by adding iron sulfate or aluminium sulfate (alum) along with sodium hydroxide, precipitates called flocs are formed. These are jelly like substances that can trap suspended particles

3. Sedimentation the flocs are settled to form sludge

4. Filtration water is passed through layers of sand and gravel to remove any remaining particles

5. Chlorination This is the sanitising process where chlorine gas is bubbled through to kill bacteria and other microbes.

6. Fluoridation Fluorine ions are added which help prevent tooth decay

These processes are used by Sydney water and are currently effective for a mass scale water supply. However there are viruses such as Giardia and Cryptosporidium that cannot be removed from the water supply. For this, the more expensive ozone sanitising with membrane filters can be used to purify the water supply.

Membrane filters essentially use a thin film of inert and synthetic polymer through which there are pores of fairly uniform size. They can be used to remove suspended particles that normal treatment processes cannot. A simple membrane filter is inert and does not react with water or corrode. It is a thin film of porous polymer. When the filter cartridge is mounted into the water pipe, the contaminates are trapped as the water flows through it

A more complex design is the capillary membrane filter where a pourous material is made into many hollow capillaries with. It has pore sizes of 02-0.5 um. Dirty water is poured on the wall of the capillary and clean water passes through.

Heavy metal pollutionIn identifying and monitoring heavy metal pollution of water, AAS is the most effective and quickest means of determining the concentration of heavy metals.

Also, by adding sodium sulfide, a precipitate will indicate the presence of heavy metals. However this may identify the presence and overall concentration, it may not work if the concentration is too low.

Heavy metals that are dangerous include Pb, Hg, Cd, Cr, Zn,

Eutrophication

This is the process where excess nutrients from phosphates and nitrates cause a subsequent algal bloom.

Effects

Water becomes unsuitable for its normal uses

It creates cyanobacteria that process poisons which is harmful for humans accessing the water way and livestock

The abundance of algae increases the BOD which, even though it generates oxygen during daylight, consumes DO from the water at night. This may cause fish to suffocate and die. Further more once the phosphate/nitrates are used up, the algae will die and have further detrimental effects on the water way.

Suppresses photosynthetic activities of deeper plants as light cannot penetrate as far in the water. It also interferes with the diffusion of oxygen from the air into the water. Sources of Phosphate and Nitrate Sewage

Organic matter contains a large amount of nitrogen and phosphorus which is then converted into phosphates and nitrates

Laundry washing powder and detergents contain nitrates

Fertiliser

Fertiliser run off is the most direct way that farming contributes

Monitoring EutrophicationThis can be monitored by directly measuring the levels of phosphate in the water. This can be done spectrophotmetrically or colorimetrically.

Section ONE

Much of the work of chemists involves monitoring the reactant and products of reactions and managing reaction conditions

Outline the role of a chemist employed in a name industry or enterprise identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist uses

Identify the need for collaboration between chemists as they collect and analyse data

Gather, process and present information from secondary sources about the work of practising scientists identifying:

The variety of chemical occupations

Specific chemical occupation for a more detailed study

Describe an example of a chemical reaction such as combustion, where reactants form different products under different conditions and thus would need monitoring

Section Two

Chemical processes in industry require monitoring and management to maximise production

Identify and describe the industrial uses of ammonia

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 exothermic

Explain why the rate of reaction is increased by higher temperatures

Explain why the yield of product in the Haber process is reduced at higher temperatures using le Chateliers principle

Explain why the Haber process is based on a delicate balancing act involving reaction energy, reaction rate and equilibrium

Analyse the impact of increased pressure on the system involved in the Haber process

Explain that the use of a catalyst will lower the reaction temperature required and identify the catalyst(s) used in the Haber process

Explain why monitoring of the reaction vessel used in the Haber process is crucial and discuss the monitoring required

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 history

Section Three

Manufactured products including food, drugs and household chemicals, are analysed to determine or ensure their chemical composition

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 effect of trace elements.

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

Gather, process and present information to interpret secondary data from AAS measurements and evaluate the effectiveness of this in pollution control

Section Four

Human activity has caused changes in the composition and the structure of the atmosphere. Chemists monitor these changes so that further damage can be limited

Describe the composition and layered structure of the atmosphere

Identify the main pollutants found in the lower atmosphere and their sources

Describe ozone as a molecule able to act both as an upper atmosphere UV radiation shield and a lower atmosphere pollutant

Describe the formation of a coordinate covalent bond

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 radical

Identify the origins of chlorofluorocarbons (CFCs) and halons in the atmosphere

Identify and name examples of isomers(excluding geometrical and optical) of halo alkanes up to eight carbon alkanes

Discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems

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

Present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs

Perform a first hand investigation to measure the sulfate content of lawn fertiliser and explain the chemistry involved

Evaluate the reliability of the results of the above investigation and to propose solutions to problems encountered in the procedure

Analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and explain how this information was obtained

Identify that water quality can be determined by considering:

Concentration of common ions

TDS

Hardness

Turbidity

Acidity

DO and BOD

Section FIVE

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 the factors that affect the concentration of a range of ions in solution in natural bodies of water such as rivers and oceans

Describe and assess the effectiveness of methods used to purify and sanitise mass water supplies

Describe the design and composition of microscopic membrane filters and explain how they purify contaminated water

Gather, 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