The Production of Materials

1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances CONSTRUCT WORD AND BALANCED FORMULAE EQUATIONS OF CHEMICAL REACTIONS AS THEY ARE ENCOUNTERED Complete as encountered

GATHER AND PRESENT INFORMATION FROM FIRST-HAND OR SECONDARY SOURCES TO WRITE EQUATIONS TO REPRESENT ALL CHEMICAL REACTIONS ENCOUNTERED IN THE HSC COURSE Complete as encountered IDENTIFY THE INDUSTRIAL SOURCE OF ETHYLENE FROM THE CRACKING OF SOME OF THE FRACTIONS FROM THE REFINING OF PETROLEUM

• Petroleum industries need to balance the production of hydrocarbon fractions to suit demand • Ethylene is a high demand hydrocarbon used to make polymers; however the fractional distillation of petroleum

does not produce enough to meet our needs • Because very little ethylene is found in natural gas or crude oil, it must be produced from other hydrocarbons by

a process known as ‘cracking’ • Fractions used are higher molecular mass fractions for which there is less market demand. Products of cracking

include short chain alkanes that can be used as petrol, and alkenes, particularly ethylene.

Cracking: a chemical process by which hydrocarbons with higher molecular mass are converted to hydrocarbons of lower molecular mass. Thermal/Steam Cracking:

• Steam and alkanes are passed through metal coils. The steam removes carbon deposits from the metal coils and the heat breaks bonds forming ethylene from alkanes.

Catalytic Cracking

• C10H22(g) 𝑧𝑒𝑜𝑙𝑖𝑡𝑒 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡�⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯� C8H18(g) + C2H4(g)

• Zeolite catalysts are aluminosilicates consisting of aluminium, silicon and oxygen o Effective because of their large surface area per unit of mass. o The zeolite catalysts adsorb the reactants, weakening their bonds and reducing activation energy for the

reaction • Can be carried out at lower temperature (500⁰C) than steam cracking, and with greater control of products

formed Pg 1-2

IDENTIFY THAT ETHYLENE, BECAUSE OF THE HIGH REACTIVITY OF ITS DOUBLE BOND, IS READILY TRANSFORMED INTO MANY USEFUL PRODUCTS As an alkene, ethylene is unsaturated and has a double C=C bond, unlike the single C-C bonds of alkanes. The main reactions that alkanes can undergo are combustion, and UV-induced halogenation. In alkenes, the double bond can be changed into a single bond, giving each carbon atom an extra bonding capacity with which ethylene can form new bonds with other molecules/atoms, in an addition reaction

• These products include a range of very useful products such as ethanol, pharmaceuticals, explosives, insecticides and the starting materials of several important plastics / polymers.

• Addiction reactions are characteristic of alkenes. • Addiction reaction: two new atoms or molecules are ‘added’ across the double bond, one to each carbon atom

linked by the double bond. This converts the C=C double bond to a C-C single bond. • Addition polymer: A long chain formed from the bonding

together of smaller molecules (monomers) in which no other product is formed. Unlike condensation polymers in which small molecules are released, all atoms present in the monomer are also present in the polymer.

• Hydrogenation: addition of hydrogen CH2=CH2(g) + H2(g) CH3-CH3(g)

Ethylene + hydrogen ethane

Heating ethylene with hydrogen in presence of metal catalyst e.g. nickel

• Halogenation: addition of halogens o These reactions are useful for distinguishing

between saturated hydrocarbons e.g. alkanes, and unsaturated hydrocarbons e.g. alkenes

o Unsaturated hydrocarbons decolourise yellow-brown bromine water

o Alkanes will not react unless exposed to ultraviolet light (substitution reactions)

CH2=CH2(g) + Br2(aq) + H2O(l) CH2OH-

CH2Br + HBr(aq)

Ethylene + bromine dissolved in water 2-

bromoethanol + hydrogen bromide

*1,2-dibromoethane may also be produced

o Reaction of ethylene with chlorine produces 1,2-dichloroethane, which is used to manufacture chloroethylene, and then PVC

o 1,2-dibromoethane used as a petrol additive • Hydrohalogenation: addition of hydrogen halides

CH2=CH2(g) + HCl(g) CH3-CH2Cl(l)

Ethylene + hydrogen chloride chloroethane

• Hydration: addition of water o Ethanol is prepared industrially from ethylene by addition of water in presence of sulfuric acid catalyst

CH2=CH2(g) + H2O(l) CH3-CH2OH(l)

Ethylene + water ethanol o Ethanol can be used as a disinfectant, anti-freeze, industrial solvent and even an alternate fuel source

for vehicles • Oxidation

o C2H4 + ½ O2 𝐴𝑔 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡�⎯⎯⎯⎯⎯⎯⎯� CH2OCH2

Ethylene + oxygen ethylene oxide

o CH2OCH2 + H2O 𝐻+�� CH2OH-CH2OH

Ethylene oxide + water 1,2-ethanediol

o 1,2-ethanediol can be used as antifreeze in cars • Polymerisation (to make polyethylene)

Pg 3-4 IDENTIFY THAT ETHYLENE SERVES AS A MONOMER FROM WHICH POLYMERS ARE MADE • Ethylene is also used to make intermediate compounds

which can then undergo polymerisation reactions • E.g. poly(styrene), PVC • Main use of ethylene is to make the polymer poly(ethylene)

• • Polymer: large molecule consisting of small repeating units called monomers joined together by covalent bonds • Polymerisation: chemical reaction by which monomers become linked to form polymers IDENTIFY POLYETHYLENE AS AN ADDITION POLYMER AND EXPLAIN THE MEANING OF THIS TERM • Addition polymerisation: monomers add to growing polymer chain in such a way that all the atoms present in the

monomer are also present in the polymer (i.e. there is no other product) o Involve unsaturated monomers with C=C double bond joining together. o Polyethylene is an addition polymer

• Condensation polymerisation involves a reaction between two different functional groups in which a molecule of water (or some other small molecule) is eliminated and the two functional groups become linked together.

OUTLINE THE STEPS IN THE PRODUCTION OF POLYETHYLENE AS AN EXAMPLE OF A COMMERCIALLY AND INDUSTRIALLY IMPORTANT POLYMER Pg 5-7:

Product Formula Use

Polyethylene (CH 2) n Plastic

Ethylene oxide (CH 2) 2O Steriliser

1,2,-ethanediol CH2OH-CH2OH

Manufacture of polyester and PET plastics, automotive antifreeze

Ethanol C2H5 OH Disinfectant, anti-freeze, solvent and fuel for vehicles

Ethanoic acid CH3 COOH Food preservative

• LDPE: Low density polyethylene o 1000-3000 atmospheres pressure, and 300⁰C temperature, along with an initiator (organic peroxide) o Process forms low-density polyethylene which has significant branching; leading to relatively disorganised,

open structure, which lowers strength of polyethylene Initiation: Organic peroxide free radical adds on to ethylene molecule, making an initiator-ethylene

free radical Propagation: Chain lengthens as reactive molecule reacts with other ethylene molecules, forming a

long chain of molecules. Termination: Combination of two free radical chains pairs up 2 unpaired electrons, terminating

chain propagation.

• HDPE: High density polyethylene o Zeigler-Natta process uses 2-3 atmospheres pressure, 60⁰C temperature, and a catalyst o Catalyst is mixture of titanium (III) chloride and a trialkylaluminium compound o Produces a more crystalline polyethylene, which has higher density and is stronger

IDENTIFY THE FOLLOWING AS COMMERCIALLY SIGNIFICANT MONOMERS: - VINYL CHLORIDE - STYRENE BY BOTH THEIR SYSTEMATIC AND COMMON NAMES Pg 8-11: • Vinyl chloride produced from ethylene, chlorine and oxygen, using CuCl2 catalyst and 150⁰C temperature • Poly(vinyl chloride) formed from vinyl chloride, using either ‘heat’ or ‘free radical’ • Styrene produced from ethylene and benzene using aluminium chloride catalyst and heat

Monomer Polymer Common name Systematic name Common name Systematic name Ethylene Ethene Poly(ethylene) Poly(ethene) Vinyl chloride Chloroethylene

Chloroethene PVC Poly(vinyl chloride)

Poly(chloroethene)

Styrene Vinyl benzene Phenyl ethene

Ethenyl benzene Poly(styrene) Poly(ethenyl benzene)

o Always use (…) around polymer names, systematic AND common DESCRIBE THE USES OF THE POLYMERS MADE FROM THE ABOVE MONOMERS IN TERMS OF THEIR PROPERTIES Factors affecting properties of polymers:

• Average chain length: longer polymers have larger molecule mass, and hence greater dispersion forces, making them stronger

• Arrangement of chains with respect to each other: crystalline regions where molecules are closely packed result in a stronger polymer. Amorphous regions produce weaker and more flexible plastics

• Degree of branching: more branching restricts orderly arrangement, and hence reduces hardness and increases flexibility

• Cross-linking between polymer chains: covalent cross-linking in thermosetting plastics make polymer very hard and difficult to melt. When heated, these plastics decompose instead of melting.

• Functional groups in monomer units: Polar functional groups increase intermolecular forces between molecules. –OH and –NH2 groups result in hydrogen bonding, and increase hardness of the plastic. Large side-groups can stiffen the chain and decrease flexibility

• Inclusion of additives: Additives include plasticisers to soften the material, or flame retardants.

Name Properties Used for LDPE • low density, soft, flexible, transparent/translucent,

electrical insulator, thermoplastic, impermeable to water • flexible shopping bags • food wrap • squeeze botles

HDPE • high density, hard to semi-flexible, opaque, high tensile

strength, thermoplastic, impermeable to water, chemically resistant

• crinkly garbage bags • rubbish bins • milk crates

Poly(vinylchloride)

• made flame resistant and flexible with additives, impermeable to water, thermoplastic

• rigid pipes and gutters • hose pipes • electrical insulation in

house wiring • extension cords • flexible raincoats • shower curtains

Poly(styrene) • rigid, unreactive, transparent due to few crystals, when

gas added forms foam, low density, heat/cold insulator, resists high impact, thermoplastic

• tool handles • compact disc cases • foam drinking cups • heat insulation

Pg 9-11: … IDENTIFY DATA, PLAN AND PERFORM A FIRST-HAND INVESTIGATION TO COMPARE THE REACTIVITIES OF APPROPRIATE ALKENES WITH THE CORRESPONDING ALKANES IN BROMINE WATER ANALYSE INFORMATION FROM SECONDARY SOURCES SUCH AS COMPUTER SIMULATIONS, MOLECULAR MODEL KITS OR MULTIMEDIA RESOURCES TO MODEL THE POLYMERISATION PROCESS

2. Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels DISCUSS THE NEED FOR ALTERNATIVE SOURCES OF THE COMPOUNDS PRESENTLY OBTAINED FROM THE PETROCHEMICAL INDUSTRY • Biomass: organic matter derived from living organisms

• Petrochemicals are chemicals made from compounds in petroleum or natural gas. Fossil fuels are non-renewable resources.

• Currently, Australia has petroleum reserves that will last about 35 years, and natural gas reserves that will last 125 years. Fossil fuels take millions of years to accumulate, and over 95% of these are burned as a source of energy.

• As petroleum supplies diminish the cost will increase. • If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are

used up. • There is also a need to find alternative sources of fuel, because using petroleum-based fuels causes global warming

via the enhanced greenhouse effect Pg 19 EXPLAIN WHAT IS MEANT BY A CONDENSATION POLYMER A n d DESCRIBE THE REACTION INVOLVED WHEN A CONDENSATION POLYMER IS FORMED Pg 12-13: • Condensation polymerisation involves a reaction between two functional groups in which a molecule of water (or

some other small molecule) is eliminated and the 2 functional groups become linked together. • For example, when two glucose monomer molecules react through two hydroxyl groups -OH, a H-OH molecule

(water) is condensed out, leaving an -O- linking the two monomer molecules. The first two glucose molecules to join condense out an H-OH, and every glucose molecule added to the growing chain then condenses out another H-OH.

• Monomers of 6-aminohexanoic acid join by peptide links [-CO-NH-], releasing molecules of water. This forms nylon-6

DESCRIBE THE STRUCTURE OF CELLULOSE AND IDENTIFY IT AS AN EXAMPLE OF A CONDENSATION POLYMER FOUND AS A MAJOR COMPONENT OF BIOMASS • Cellulose is main constituent of plant cell walls, and major structural component of woody plants and natural fibres

e.g. cotton • Most abundant polymer in the biosphere

• Large proportion of world’s biomass is in the form of cellulose • Made up of thousands of glucose monomers • Β-linkages in cellulose (bulky CH2OH groups on alternating sides) result in formation of flat, ribbon-like strands

o Close packing of these ribbons and strong hydrogen bonds between them gives cellulose its strength and rigid structure.

• The reduced availability of hydroxyl groups in the cellulose structure, due to their involvement in hydrogen bonding

between the chains, makes it insoluble in water and resistant to chemical attack. Pg 20-21 IDENTIFY THAT CELLULOSE CONTAINS THE BASIC CARBON-CHAIN STRUCTURES NEEDED TO BUILD PETROCHEMICALS AND DISCUSS ITS POTENTIAL AS A RAW MATERIAL • A 3 carbon-chain and a 4 carbon-chain are present within the structure of a glucose monomer in a cellulose chain,

and have attached hydrogen/hydroxyl groups • Many polymers are made using 3 carbon monomers (such as polypropylene in Australian 'paper' currency) or 4

carbon monomers (such as those used to make synthetic rubbers). • The carbon-chain sections in cellulose could be changed to chemicals that at present mostly made from petroleum,

if a chemical processes can be developed or micro-organisms found that can break the cellulose into glucose monomers, and glucose into three carbon-chains and four carbon-chains.

• Thus biomass, a renewable resource, could be used to make polymers instead of fossil fuels, a non-renewable one. 1) Cellulose (Broken down by steam/acid pre-treatment, then hydrolysis using the enzyme cellulase)

o The reduced availability of hydroxyl groups in the cellulose structure, due to their involvement in hydrogen bonding between the chains, makes it insoluble in water and resistant to chemical attack.

2) Glucose (Broken down by yeast/distillation) 3) Ethanol (Broken down by catalysed dehydration) 4) Ethylene (Source for petrochemical industry)

______________________________________________________________________________ • Plastics made from cellulose would be biodegradable, biocompatible and renewable • Existing biopolymer chains in plant material can be modified

o Cellulose nitrate is a synthetically modified cellulose that was widely used for photographic and movie film early this century. It was also used as an explosive and a plastic called celluloid. Unfortunately it was highly flammable and was replaced.

o Cellulose acetate, which is much less flammable, is used today for overhead projector slides. o Rayon is another polymer derived from modified cellulose

USE AVAILABLE EVIDENCE TO GATHER AND PRESENT DATA FROM SECONDARY SOURCES AND ANALYSE PROGRESS IN THE RECENT DEVELOPMENT AND USE OF A NAMED BIOPOLYMER. THIS ANALYSIS SHOULD NAME THE SPECIFIC ENZYME(S) USED OR ORGANISM USED TO SYNTHESISE THE MATERIAL AND AN EVALUATION OF THE USE OR POTENTIAL USE OF THE POLYMER PRODUCED RELATED TO ITS PROPERTIES

• Biopolymer: a naturally occurring polymer produced by living organisms, including plants, animals and microorganisms

o Biopolymers are biodegradable, biocompatible and renewable Pg 14-19: Poly(3-hydroxybutyrate)

• Bacteria ‘Alcaligenes eutrophus’ are grown in fermentation vats with high conc. glucose, lowered conc. nitrogen, and 30⁰ temperature

• PHB produced up to 80% of bacteria’s dry weight.

• PH3B is extracted using solvents like halogenated hydrocarbons which break bacterial cell walls and separate plastic from cell debris.

• PHB is then milled to a powder/pellets • Properties and uses

o Thermoplastic: can be melted, moulded, shaped into various forms o Similar to polypropylene, but biodegradable, biocompatible and renewable o Degrades slowly in the body, and is biocompatible/non-toxic

Potentially used as controlled drug-release carrier Used in stitches/sutures

o Biodegradability is a disadvantage for many applications where the plastic must not break down over time

o Breaks down in anaerobic conditions of landfill Disposable nappies, bottles, bags, packaging materials

o Good oxygen permeability Use as wrapping film

o Similar physical properties to polypropylene: brittle, rigid, crystalline, high tensile strength, high MP Brittle nature limits its use

o Copolymers, e.g. with 3-hydroxy pentanoate (to make BioPol), are more flexible, and hence have more applications and potential use in the future

o High production costs (5-7 x petrochemical plastics) limits its use currently

3. Other resources, such as ethanol, are readily available from renewable resources such as plants DESCRIBE THE DEHYDRATION OF ETHANOL TO ETHYLENE AND IDENTIFY THE NEED FOR A CATALYST IN THIS PROCESS AND THE CATALYST USED

• Before ethylene could be produced from catalytic cracking of petroleum, ethylene was produced primarily from dehydration of ethanol

o Dehydration: chemical reaction where water is removed from a compound o Heating ethanol vapour over a catalyst at 350⁰C. o Effectively, the –OH group is removed, a hydrogen atom is removed from an adjacent carbon atom,

which form a water molecule o This leaves the adjacent carbon atoms with an unfilled outer shell, changing their C-C single bond to a

C=C double bond. • In the past, aluminium oxide catalyst was used; today porous ceramic crystals are used • Catalyst is needed because the ethanol molecule is stable, and will not spontaneously break bonds to release

a water molecule and form a double bond. • As a dehydrating agent, sulfuric acid removes water , promoting the forward reaction (Le Chatelier’s Principle) • In the lab, catalyst used is an excess of concentrated sulfuric acid, or phosphoric acid

o A zeolite catalyst can also be used, which provides very reactive site • 350⁰C temperature, (ethanol is in gaseous state)

o C2H5OH(g) C2H4(g) + H2o(g) DESCRIBE THE ADDITION OF WATER TO ETHYLENE RESULTING IN THE PRODUCTION OF ETHANOL AND IDENTIFY THE NEED FOR A CATALYST IN THIS PROCESS AND THE CATALYST USED

• Ethanol can be made in 2 ways: fermentation of sugars, hydration of ethylene o Hydration: chemical reaction where water is added to a compound

o Most industrial ethanol is made by hydration since ethylene is a low-cost material • Reverse of dehydration of ethanol

o Reaction is carried out with an excess of high-pressure steam • Catalyst is needed because water molecule itself will not attack the electrons in the ethylene double bond

o The electron-rich double bond is likely to be attacked by an ion that has an electron deficiency (e.g. H+ ion); and so acid catalysts are used

o Also, the reaction occurs very slowly without a catalyst; a catalyst is needed to make the reaction proceed at a fast rate by lowering activation energy

• Catalyst used is dilute sulfuric acid • 300⁰C temperature (water in the form of steam) • In industry, highly acidic zeolite catalysts are used instead, due to problems with safety and environment when

using sulfuric acid o C2H4(g) + H2O(g) C2H5OH(g)

PROCESS INFORMATION FROM SECONDARY SOURCES SUCH AS MOLECULAR MODEL KITS, DIGITAL TECHNOLOGIES OR COMPUTER SIMULATIONS TO MODEL:

- THE ADDITION OF WATER TO ETHYLENE - THE DEHYDRATION OF ETHANOL

DESCRIBE AND ACCOUNT FOR THE MANY USES OF ETHANOL AS A SOLVENT FOR POLAR AND NON-POLAR SUBSTANCES

• Ethanol is a common solvent in cosmetics (perfume), solvent-based paints, dyes, food colourings, household cleaning products, pharmaceuticals, and in industry

• Sold domestically as methylated spirits o 95% ethanol, 5% poisonous methanol, and some foul-tasting chemicals to discourage people from

drinking it. Called denatured ethanol • The –OH end is polar (hydrophilic), because the C-O and O-H bonds are polar, due to oxygen’s high

electronegativity o Ethanol dissolves polar substances such as chloroform, CHCl3, and common ether with dipole-dipole

forces o Can form hydrogen bonds with many other substances, and so can dissolve these [mostly organic]

substances readily E.g. glucose, sucrose, carboxylic acids, amino acids, and some proteins Because of hydrogen bonding, ethanol is miscible with water in any proportion. [completely

miscible] • Because the alkyl part (CH3-CH2-) is non-polar (hydrophobic), ethanol can also dissolve non-polar substances,

as it forms dispersion forces between hydrocarbon end and non-polar substance o Allows ethanol to dissolve non-polar iodine, and short-chain hydrocarbons like pentane/heptane o Miscible in hexane as well as water

• If hydrocarbon chain was lengthened (e.g. pentanol), it could not dissolve in water; if hydrocarbon chain was shortened (e.g. methanol), it would not be miscible in other hydrocarbons

• *Ethanol is used as a solvent in dissolving substances that do not dissolve easily in water. Once the non-polar material is dissolved in the ethanol, water is added to prepare a solution that is mostly water.

o E.g. perfumes: *Since ethanol has a lower boiling point, it quickly evaporates off the skin due to body heat, leaving the necessary fragrant chemicals on the skin.

• *Used in household cleaning products, because the non-polar alkyl end forms dispersion forces with non-polar grease, then polar –OH end allows the cleaning solution/grease to be washed away by water

o *Ethanol is least toxic of the alkanols

Ethanol can form hydrogen bonds with water:

OUTLINE THE USE OF ETHANOL AS A FUEL AND EXPLAIN WHY IT CAN BE CALLED A RENEWABLE RESOURCE • Ethanol can undergo combustion, and may be used as a fuel

o Combustion generates 1367 kJ of heat per mole of ethanol • Blending ethanol with petrol (e.g. E10) produces fuels that produce less pollution, contribute less to the

greenhouse effect, and reduce the use of non-renewable petroleum supplies o Presence of oxygen in ethanol itself leads to cleaner combustion and less soot/carbon monoxide

• Ethanol can also be used as a portable fuel for camping stoves, in the form of methylated spirits • Ethanol is a renewable resource

o Can be made from glucose, unlike petrol which is made from limited petroleum supplies Glucose is obtained from plant material with a high starch/simple-sugar content

• E.g. wheat, maize, potatoes, grapes, molasses, sugar cane • Since plant matter is a renewable resource, ethanol is a renewable resource

o When burnt, it forms carbon dioxide and water; these were used in the production of ethanol (they are the reactants for photosynthesis in plants), and so can be converted back into ethanol

o Ethanol, after being broken down into carbon dioxide and water via combustion, can ultimately reformed back into ethanol, and hence can be called a renewable resource

DESCRIBE CONDITIONS UNDER WHICH FERMENTATION OF SUGARS IS PROMOTED

• Suitable source of sugar mashed up with water (in this case sugar cane) • Yeast added • Very low concentrations of oxygen to prevent aerobic respiration

o A small concentration of oxygen must be provided to the fermenting yeast as it is a necessary component in the biosynthesis of polyunsaturated fats and lipids

• Small amount of yeast nutrients such as phosphate salts • Mixture kept at 37⁰C

o Note*: fermentation is an exothermic process • Mixture kept in the dark

SUMMARISE THE CHEMISTRY OF THE FERMENTATION PROCESS a n d PRESENT INFORMATION FROM SECONDARY SOURCES BY WRITING A BALANCED EQUATION FOR THE FERMENTATION OF GLUCOSE TO ETHANOL

• Cane sugar waste is rich in sucrose. If water and yeast are added, the sucrose reacts with water producing glucose and fructose, which can be fermented by the yeast.

o C12H22O11 + H2O C6H12O6 + C6H12O6

o Sucrose + water glucose + fructose

• Fermentation

o C6H12O6(aq) 𝑦𝑒𝑎𝑠𝑡�⎯⎯� 2 C2H5OH(aq) + 2 CO2(g)

o Glucose/fructose ethanol + carbon dioxide

SOLVE PROBLEMS, PLAN AND PERFORM A FIRST-HAND INVESTIGATION TO CARRY OUT THE FERMENTATION OF GLUCOSE AND MONITOR MASS CHANGES DEFINE THE MOLAR HEAT OF COMBUSTION OF A COMPOUND AND CALCULATE THE VALUE FOR ETHANOL FROM FIRST-HAND DATA Molar heat of combustion: the heat liberated when one mole of a substance undergoes complete combustion to produce CO2 and H2O under standard conditions of temperature and pressure. IDENTIFY DATA SOURCES, CHOOSE RESOURCES AND PERFORM A FIRST-HAND INVESTIGATION TO DETERMINE AND COMPARE HEATS OF COMBUSTION OF AT LEAST THREE LIQUID ALKANOLS PER GRAM AND PER MOLE ASSESS THE POTENTIAL OF ETHANOL AS AN ALTERNATIVE FUEL AND DISCUSS THE ADVANTAGES AND DISADVANTAGES OF ITS USE ADVANTAGES:

• Ethanol is a renewable resource, and would reduce usage of non-renewable fossil fuels (if less fossil fuel was used to make ethanol than would normally be used as a fuel)

o Made from glucose (crops), unlike petrol which is made from limited petroleum supplies Local oil reserves expected to run out in a few decades, so using renewable ethanol fuel, can

make petroleum supplies last longer • Saving petroleum for petrochemicals

o When burned, it forms carbon dioxide and water; these were used in the production of ethanol, and can be converted back into ethanol

• Using ethanol would reduce greenhouse gas emissions (if less CO2 was released in production of ethanol than would normally be released from the combustion of fossil fuels)

o Carbon dioxide liberated by combustion of ethanol, was absorbed from atmosphere by crops from which ethanol is produced i.e. ethanol is ‘CO2 neutral’, whereas burning fossil fuels releases carbon dioxide which was

trapped underground • Cars using ethanol fuel produce fewer pollutants, especially carbon monoxide, than cars running on petrol

o One mole of octane requires more oxygen to burn than one mole of ethanol. Hence, petrol is more likely to undergo incomplete combustion than ethanol.

o Also, oxygen in ethanol provides oxygen for combustion reaction, allowing complete combustion to occur. Reduces carbon monoxide and soot emissions, and hence pollution

o Toxic ‘anti-knock’ additives such as MTBE that provide oxygen don’t need to be added to the fuel DISADVANTAGES:

• Ethanol may not be a renewable resource o More fossil fuels may need to be burned for the energy used in the production of ethanol, than is saved

by using ethanol as a fuel instead of fossil fuels • Ethanol may not reduce greenhouse gas emissions

o More energy is needed to grow the crops, fertilise them, transport them, and for the distillation process7 This energy would most likely come from the combustion of fossil fuels If this is compared to carbon dioxide released by combustion of octane, more carbon dioxide is

produced per unit of energy produced by ethanol, than by octane o Hence, ethanol as a fuel may contribute more to the greenhouse effect than petrol.

Currently, there have been no reliable studies to show whether ethanol made in Australia produces less greenhouse gas overall than the petrol it replaces

• Large areas of agricultural land would be needed to grow suitable crops o Environmental problems such as soil erosion, deforestation, fertiliser runoff and salinity o Habitat loss o Reduces area available for subsistence food crops

• Disposal of smelly waste fermentation liquors after the removal of ethanol presents environmental problems • Petrol with more than 10-20% ethanol has detrimental effect on vehicles

o Engines and fuel lines must be modified to use 100% ethanol, because ethanol is corrosive, and has different burn characteristics Cost of setting up factories to make a totally new engine design, makes 100% ethanol unlikely in

the near future Ethanol has a high potential as an alternative fuel, mainly because it is a renewable resource. It is made from sugars present in sugar cane, maize, molasses, etc. As such, it can reduce the use of dwindling petroleum supplies. Also, combustion of ethanol is neutral with respect to the greenhouse effect. Cars running on ethanol also release less carbon monoxide and soot, as the oxygen from ethanol promotes complete combustion without toxic additives such as MTBE. However, with current technology, the fossil fuels used and carbon dioxide released in the production of ethanol from crops may outweigh the amount of fossil fuel usage that ethanol replaces. Therefore, ethanol as an alternative fuel is currently not much better than oil from a greenhouse effect viewpoint. Other disadvantages include the large areas of arable land which would be needed to grow suitable crops, and the disposal of the smelly waste fermentation liquors after the removal of ethanol, both of which present environmental problems. Economic feasibility has also limited the use of ethanol as an alternative fuel in the past. However, in light of increasing awareness of climate change, the greenhouse effect, and our dwindling petroleum supplies, ethanol has a good potential as an alternative fuel, especially if efficient production of glucose from cellulose can be done, and renewable energy sources used to provide energy for the production processes, e.g. solar energy for distillation. Genetic engineering of yeast to increase ethanol concentration to greater than 15% is also an area of active research. PROCESS INFORMATION FROM SECONDARY SOURCES TO SUMMARISE THE PROCESSES INVOLVED IN THE INDUSTRIAL PRODUCTION OF ETHANOL FROM SUGAR CANE

• Sugarcane is mashed/shredded, and mixed with water • Cane juice mixed with lime to adjust pH to about 7 • Cane juice is concentrated until sugar crystallises out

• Centrifuge is used to separate sugar from molasses (the remaining liquid) • *Blackstrap molasses collected as by-product of the manufacture of cane sugar

o Ethanol produced from a normally useless waste product • Molasses diluted to a less concentrated mash • pH adjusted to about 4-5 using mineral acid • Yeast is added, and fermentation occurs for 1-3 days

o Conditions for fermentation Suitable source of sugar mashed up with water (in this case sugar cane) Yeast added Very low concentrations of oxygen to prevent aerobic respiration

• A small concentration of oxygen must be provided to the fermenting yeast as it is a necessary component in the biosynthesis of polyunsaturated fats and lipids (0.05 – 0.10 mm Hg oxygen tension)9

Mixture kept at 37⁰C Small amount of yeast nutrients such as phosphate salt1

o Yeasts are susceptible to ethanol inhibition; growth rate halts at 10%, cells die at 14% due to ethanol toxicity

o Zymase is the ‘enzyme complex’ which catalyses the reaction o Yeast used is Saccharomyces Cereviciae o 90-95% of theoretical yield is produced, as some of the substance is used up by the yeast o Fermentation is an exothermic process

o C6H12O6(aq) 2CH3CH2OH(aq) + 2CO2(g) • Fermented product (6-10% ethanol) is sent to the purification section • Fractional distillation of the ethanol/water produces a higher concentration of ethanol (96%)

o Distillation takes about half of the energy released when ethanol is burned In the future, low energy methods may be used such as passing the solution through zeolite

filters which act as molecular sieves • Polar water molecules attracted to polar parts of zeolite, while less polar ethanol passes

through o Alternative dehydration processes may be used to concentrate ethanol higher than 96% such as:

Azeotropic distillation by adding benzene

• For alternative sources of biomass other than sugar cane, acids and cellulase enzymes are some of the ways that are being looked into to hydrolyse the more complex carbohydrates (e.g. cellulose) in the crop into simpler sugars such as sucrose and glucose.

PROCESS INFORMATION FROM SECONDARY SOURCES TO SUMMARISE THE USE OF ETHANOL AS AN ALTERNATIVE CAR FUEL, EVALUATING THE SUCCESS OF CURRENT USAGE

• In 1970’s, Brazil attempted to grow sugar cane to supply ethanol as a fuel o Purpose: to reduce consumption of non-renewable fuels, and to use locally produced and plentiful

sugar cane instead of expensive imported oil o Brazilian government subsidised production of ethanol by sugar cane fermentation. o At peak in 1980s, Brazil produced 16 billion litres of fuel ethanol per year. o Disrupted food production farming to make way for ‘ethanol farming’ and was an economic failure

1990: Ethanol shortage and lowered oil prices resulted in consumers switching back to petrol-ethanol mixtures.

o As oil prices increase again, consumers are shifting again towards using ‘flex-fuel’ vehicles that can run on any proportion of ethanol and petrol

• Petrol with 10-20% ethanol can be used in ordinary engines without any modification

o Car manufacturers oppose higher than 10% ethanol in petrol on the grounds that it has a detrimental effect on vehicles. Fuel with 10% ethanol, 90% petrol, is called E10.

o Federal government planning to restrict petrol to contain no more than 10% ethanol o Engines must be modified to use 100% ethanol, because ethanol is corrosive, and has different burn

characteristics *Cost of setting up factories to make a totally new engine design, makes 100% ethanol unlikely

in the near future

• Devoting large areas of land to growing crop (monocropping) for the production of ethanol may not be economically feasible in a modern context

o Currently in Australia, sugar cane wastes are the source of sugars for fermentation to ethanol Use of sugar industry wastes (molasses) is not enough to totally replace petrol with ethanol

o Some argue that using agricultural land and crops for fuel production, has caused food prices to skyrocket in recent times A UN report says that biofuels have caused world food prices to go up by 75%

• Ethanol costs more than petrol to produce, even though it can be made from waste products like molasses

o Australian government has set up subsidies to encourage production of ethanol to be added to petrol o Distillation takes about half of the energy released when ethanol is burned o Most of the agricultural products used to produce ethanol, command higher prices as food o Agricultural products often have a low ethanol yield, and high transport costs

• Use of 100% ethanol fuel seems unlikely, unless: o Efficient production of glucose from cellulose (crop wastes) can be done o Renewable energy sources used to provide energy for distillation process

• Cars using ethanol fuel produce fewer pollutants, especially carbon monoxide, than cars running on petrol o One mole of octane requires more oxygen to burn than one mole of ethanol. Hence, petrol is more likely

to undergo incomplete combustion than ethanol. o Also, oxygen in ethanol provides oxygen for combustion reaction, allowing complete combustion to

occur Reduces carbon monoxide and soot emissions, and hence pollution

o Toxic additives such as MTBE that provide oxygen don’t need to be added to the fuel IDENTIFY THE IUPAC NOMENCLATURE FOR STRAIGHT-CHAINED ALKANOLS FROM C1 TO C8 Methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol

4. Oxidation-reduction reactions are increasingly important as a source of energy EXPLAIN THE DISPLACEMENT OF METALS FROM SOLUTION IN TERMS OF TRANSFER OF ELECTRONS • Displacement reactions: oxidation-reduction reactions in which one of the products is displaced from solution as a

separate phase • Metal displacement reactions: Oxidation-reduction reactions in which one metal reduces the ions of another metal

into a neutral atom displacing it from solution as a separate phase, and itself becomes an ion • E.g. iron nail dissolves when placed in a solution of copper sulphate

o Fe(s) + Cu2+(aq) Fe2+

(aq) + Cu(s)

o Transfer of electrons from iron metal to copper(II) ions, occurs on the surface of iron nail o This occurs because Cu2+ ions have a

greater tendency to gain electrons than Fe2+ ions, and so Cu2+ ions will accept electrons from Fe metal.

Pg 23:

• More active metal displaces less active metal from solution, because a more active metal atom loses one or more electrons to become a cation. These electrons are transferred to the less active metal, reducing it into elemental form

IDENTIFY THE RELATIONSHIP BETWEEN DISPLACEMENT OF METAL IONS IN SOLUTION BY OTHER METALS TO THE RELATIVE ACTIVITY OF METALS

• Metals can be arranged into an activity series by their ability to displace one another from solution • An activity series is a list of metals arranged in order of decreasing ease of oxidation

o Any metal can be oxidised by the ions of a less reactive metal Pg 23:

• The more reactive a metal, the more readily it gives up electrons. Metals which have a greater tendency to give up electrons are more reactive than those that have a lesser tendency to give up electrons

• A more active metal will displace the metal ion of a less active metal from solution, because it gives up electrons more easily than the ion.

ACCOUNT FOR CHANGES IN THE OXIDATION STATE OF SPECIES IN TERMS OF THEIR LOSS OR GAIN OF ELECTRONS

• Oxidation states help us keep track of the number of electrons transferred in oxidation-reduction reactions o The oxidation state of an element in a compound is the number of electrons transferred to or from

the neutral atom when the compound is formed • An increase in oxidation state represents oxidation, so an atom must lose electrons to increase its oxidation

state o Oxidation states are therefore a useful way of determining whether an oxidation-reduction reaction has

taken place.

Oxidation States: - of elements in their elemental form is 0 including diatomic elements O2 - of neutral compounds is 0 - sum of oxidation states of atoms in a neutral compound equals 0 - oxidation state of ion, or the sum of oxidation states of atoms in the radical, equals the charge - of oxygen is -2 except peroxide is -1 - of hydrogen is +1 except hydride is -1

Pg 24:

• Oxidation: a loss of electrons, increase in oxidation number, loss of hydrogen or gain of oxygen • Reduction: a gain of electrons, decrease in oxidation number, gain of hydrogen or loss of oxygen

DESCRIBE AND EXPLAIN GALVANIC CELLS IN TERMS OF OXIDATION/REDUCTION REACTIONS a n d

OUTLINE THE CONSTRUCTION OF GALVANIC CELLS AND TRACE THE DIRECTION OF ELECTRON FLOW

• Description of galvanic cell o Consists of 2 half-cells. Each half-cell consists of an electrode (conductive metal/graphite strip in contact

with an electrolyte solution). Electrolyte solutions are joined by salt bridge containing an electrolytic solution e.g. KNO3. Salt bridge may consist of filter paper saturated with KNO3 solution. External circuit connects the electrodes in the two half-cells

• In terms of oxidation/reduction reactions o A galvanic cell physically separates oxidation and reduction reactions, so that the movement of

electrons occurs through an external circuit (constituting a current). A salt bridge connects the two half-cells to carry charged ions in solution. A galvanic cell is thus composed of two half-cells, a reductant half-cell where oxidation occurs (anode) and an oxidant half-cell where reduction occurs (cathode).

• Oxidation always occurs at the anode

o For a galvanic cell, the anode is negative (electrons produced) • Reduction always occurs at the cathode

o For a galvanic cell, the cathode is positive (electrons accepted) • Daniel cell: reaction between metallic zinc and copper(II) sulphate

o Zinc ions go into solutions and hence zinc strip slowly dissolves o Zn(s) Zn2+

(aq) + 2e- o Electrons given up by zinc pass through external circuit to copper strip. At the cathode they’re accepted

by copper(II) ions in solution, reducing them to copper atoms which deposit on the strip. Removal of Cu2+ ions from solution causes a colour change from blue to colourless

o Cu2+(aq) + 2e- Cu(s)

o For each zinc ion produced, a copper(II) ion is removed from solution. Electrical neutrality in solutions is maintained by migration of positive ions towards copper half-cell and negative ions towards zinc half-cell Zn2+ ions move into salt

bridge, NO3- ions move

into zinc half-cell SO4

2- ions move into salt bridge, K+ ions move into copper half-cell

Cell diagram: Zn | Zn2+ || Cu2+ | Cu • The single vertical line represents the

boundary between phases. The double vertical line represents a salt bridge through which ions can move

• Pt, H2(g) | H+ || Au3+ | Au o Anode is hydrogen gas bubbling

over platinum electrode, in H+ solution. Cathode is gold electrode dipping into Au3+ solution

• Pt, H2(g) | H+, Cl- | Cl2(g), Pt o Cathode is hydrogen gas bubbling over platinum electrode. Anode is chlorine gas bubbling over

platinum electrode. Both electrodes share a common HCl(aq) electrolyte. There is no double line || because there is no salt bridge.

• Pt | I2, I- || Fe3+, Fe2+ | Pt

o Cathode is platinum electrode dipping into solution of iodine and iodide ions. Anode is platinum electrode dipping into solution of Fe3+ and Fe2+ ions. There is no single vertical line | between Fe3+ and Fe2+ because they are in the same phase. Rather, the boundary between phases is between the platinum electrode, and the solution of both iron ions.

• The zinc electrode alone is denoted by Zn | Zn2+ Pg 26-28:

• Function of salt bridge: o To complete the circuit o Allows movement of ions to neutralise build-up of ions in each beaker.

• *If one reactant is going from elemental to ionic, and the other from ionic to elemental form, then two beakers with two electrolyte solutions are needed, as the initially ionic reactant may directly react with the initially elemental one.

o E.g. If Zn|| Cu galvanic cell had a common electrolyte, zinc metal would directly displace copper ions • *If both reactants are going from elemental to ionic state, then one beaker with a common electrolyte solution

may be used, as the reactants cannot react with each other directly since they’re physically separated initially, and neither the elemental anode or cathode can react directly with any ions in the common electrolyte

o E.g. H2||Cl2 galvanic cell Pg 26-28:

• Direction of electron flow is from anode to cathode DEFINE THE TERMS ANODE, CATHODE, ELECTRODE AND ELECTROLYTE TO DESCRIBE GALVANIC CELLS Pg 26-28:

• Anode: Electrode at which oxidation occurs • Cathode: Electrode at which reduction occurs • Electrode: Electrical conductors in contact with electrolyte solution; the interface where oxidation/reduction

occurs (often made of metal, graphite, or inert platinum) • Electrolyte: any substance containing mobile ions that behaves as an electrically conductive medium

o In the case of galvanic cells, these are the ionic solutions. The electrolyte must not react with any ions in the 2 solutions it is connecting.

PERFORM A FIRST-HAND INVESTIGATION TO IDENTIFY THE CONDITIONS UNDER WHICH A GALVANIC CELL IS PRODUCED PERFORM A FIRST-HAND INVESTIGATION AND GATHER FIRST-HAND INFORMATION TO MEASURE THE DIFFERENCE IN POTENTIAL OF DIFFERENT COMBINATIONS OF METALS IN AN ELECTROLYTE SOLUTION GATHER AND PRESENT INFORMATION ON THE STRUCTURE AND CHEMISTRY OF A DRY CELL OR LEAD-ACID CELL AND EVALUATE IT IN COMPARISON TO ONE OF THE FOLLOWING:

- BUTTON CELL - FUEL CELL - VANADIUM REDOX CELL - LITHIUM CELL - LIQUID JUNCTION PHOTOVOLTAIC DEVICE (EG THE GRATZEL CELL)

IN TERMS OF: - CHEMISTRY - COST AND PRACTICALITY - IMPACT ON SOCIETY - ENVIRONMENTAL IMPACT

• Pg 30-35

Dry Cell (Leclanché Cell) Fuel Cell Cost & Practicality • Cheap to produce

• Can be used for a variety of things • Fairly large for their small voltage

(1.5V) • Can leak • Slowly go flat as voltage drops off

gradually • Short shelf life because zinc anode

reacts with acidic NH4+ ions

• If current is drawn rapidly, NH3 gas builds up, causing a drop in voltage

• Primary cells: cannot be recharged

• Continuous supply of <1.23V • High fuel efficiency (80-90%) • Long operating lifetime (50,000 hours) • Expensive as it is a developing technology • Auxiliary systems that feed reactants into

cell and remove products are expensive • Liquid cooling systems needed • Pure hydrogen required, as impurities

poison Pt catalyst • Theoretical e.m.f. of 1.23 V hard to

achieve, as movement of H+ ions through electrolyte is a limiting factor

Impact on Society • Many portable devices can be used • Long operating lifetime (50,000 hours)

without mains power supply • Changed our way of life: efficient,

cheap, easily transportable devices e.g. radios

• Resulted in a much more mobile society

• Developing technology for hydrogen fuel that may replace petroleum fuel

• Used in space shuttles

Environmental Impact • Chemicals within a dry cell are not as damaging to environment as other chemicals in other batteries

• Zinc, a heavy metal, is toxic to animals

• Since these are primary cells, they can take up a lot of space in landfills, where build-up of chemicals like zinc can occur

• Non-polluting, as only water is produced • Hydrogen and oxygen reactants are

plentiful • Storage of explosive hydrogen required

SOLVE PROBLEMS AND ANALYSE INFORMATION TO CALCULATE THE POTENTIAL REQUIREMENT OF NAMED ELECTROCHEMICAL PROCESSES USING TABLES OF STANDARD POTENTIALS AND HALF-EQUATIONS Pg 29:

• Only potential difference between two cells coupled together can be measured. It is necessary to use a reference half-cell, so that individual half-cell potentials can be compared

• The hydrogen half-cell consists of hydrogen gas at a pressure of 1 atmosphere, bubbling around an inert platinum electrode in a solution of 1M hydrogen ions:

• Hydrogen half-cell is given an value of 0.00 V • The standard reduction potential, , of an electrode, is the potential of that electrode in its standard state

(1M for any solutes, 1 atm for any gases) relative to the standard hydrogen electrode, with standard conditions of 101.3 kPa pressure and 25⁰C temperature

• A positive value means that an electrode has a greater tendency to accept electrons and be reduced than the hydrogen system. A negative value means that an electrode has a greater tendency to lose electrons and be oxidised than the hydrogen system.

• values are not voltages, they are a measure of electromotive force (e.m.f.). The e.m.f. of a galvanic cell is the potential difference across the electrodes when a negligibly small current is being drawn.

5. Nuclear chemistry provides a range of materials DISTINGUISH BETWEEN STABLE AND RADIOACTIVE ISOTOPES AND DESCRIBE THE CONDITIONS UNDER WHICH A NUCLEUS IS UNSTABLE Pg 37-38:

• A stable isotope’s nucleus doesn’t change • A radioactive isotope has an unstable nucleus which releases particles/energy to become more stable.

o Any isotope with atomic number > 83, is unstable o Stability of nucleus also depends on neutron-to-proton ratio. o Most stable nuclei are found in an area of graph known as the ‘zone of stability’

• Radioactivity is the spontaneous change in composition of an unstable nucleus leading to the emission of radiation.

• Alpha-decay o Occurs when there are too many protons AND

neutrons (nucleus too heavy) U-238: 238

92U 23490Th + 42He

• Beta-decay o Occurs when there are too many neutrons for

the # of protons present. A neutron turns into a proton and electron

o Mass number remains same, atomic number +1, electron emitted Carbon-14: 14

6C 147N + 0-1e

• Positron emission o Occurs when there are too many protons for

the # of neutrons present. A proton becomes a neutron and positron

o Mass number remains same, atomic number -1, positron emitted K-38: 38

19K 3818Ar + 01e

• Electron capture Occurs when there are too many protons for the # of neutrons present. An inner-orbital electron is captured by the nucleus, converting a proton into a neutron

Hg-201: 20180Hg + 0-1e 201

79 Au • Gamma radiation

o Emission of high energy photons enables nucleus to lose excess energy and become more stable

DESCRIBE HOW TRANSURANIC ELEMENTS ARE PRODUCED Pg 38:

• Transuranic elements are those that follow uranium in the periodic table. Uranium has the highest atomic number of a natural element (92)

• Elements of atomic number >92, have to be made synthetically by bombarding nuclei with neutrons in a nuclear reactor, or with charged nuclei e.g. α particles in a particle accelerator.

• Neptunium and plutonium were synthesised by bombarding uranium-238 with neutrons o 238

92U + 10n 23992U 239

93Np + 0-1e 239

93Np 23994Pu + 0-1e

• Only three of the transuranic elements, those with atomic numbers 93, 94 and 95, have been produced in nuclear reactors.

• Transuranic elements from atomic number 96 and up are all made by accelerating a small nucleus (such as He, B or C) in a charged particle accelerator to collide with a heavy nucleus (often of a previously made transuranic element) target.

DESCRIBE HOW COMMERCIAL RADIOISOTOPES ARE PRODUCED

• In induced nuclear transformations, the target nucleus is bombarded with various particles. These particles may become incorporated within the target nucleus, creating a new unstable nuclide.

Pg 39-40:

• Nuclear reactors produce neutron-rich radioisotopes o Neutrons are uncharged and so don’t need to be accelerated, to be absorbed o Source of neutrons is by fission reactions in fission reactor

o Sample to be irradiated is placed in the core of the reactor, where it absorbs neutrons.

o 9842Mo + 10n 99

42Mo 99

42Mo 99m43Tc + 0-1e

99m43Tc 99

43Tc + γ

o ANSTO operates the HIFAR nuclear reactor at Lucas Heights • Particle accelerators produce neutron deficient radioisotopes

o An accelerator is needed to overcome electrostatic repulsion, so that target nucleus can be bombarded with a charged particle

o Cyclotron: Used to produce radioisotopes for medical use Charged particles are accelerated in a spiral path

o 9842Mo + 21H 99m

43Tc + 10n

ANSTO operates the National Medical Cyclotron at Sydney’s Royal Prince Alfred Hospital o Synchrotron: Used in research into the composition of materials

Can accelerate protons to 90% of speed of light o Linear accelerators: Used for radiation therapy and physics research

Produces high-energy electrons IDENTIFY INSTRUMENTS AND PROCESSES THAT CAN BE USED TO DETECT RADIATION Scintillation counter: Low energy radiation that is too weak to ionise atoms is called non-ionising radiation and can be detected by a scintillation counter. The non-ionising radiation transfers energy to a fluorescent molecule that emits light. A photomultiplier produces an amplified electrical pulse from the light. A counter counts the pulses. Pg 44-45:…

PROCESS INFORMATION FROM SECONDARY SOURCES TO DESCRIBE RECENT DISCOVERIES OF ELEMENTS

• The nineteen transuranic elements with the atomic numbers above 95 require high-energy particle accelerators to be produced.

• Heaviest element produced as of 2005 is element 116, with the IUPAC systematic name of ununhexium (symbol Uuh). This was produced in 2000 by bombarding curium atoms with calcium nuclei

o 24896Cm + 48

20Ca 292116Uuh + 41

0n

• Element 110 (Darmstadtium) (Ds) was made in collision between lead and nickel nuclei o First discovered at GSI in 1994, but different observations produced different isotopes of the new

element o In 1998, GSI team produced 271

110Ds, by accelerating a beam of nickel-64 nuclei to an energy of 209 MeV and directly it at a lead-208 target

o The team observed alpha-decay sequences which signalled production and decay of 271110Ds

o 20882Pb + 64

28Ni 271110Ds + 10n

IDENTIFY ONE USE OF A NAMED RADIOISOTOPE:

- IN INDUSTRY - IN MEDICINE

Pg 41-43:

• In industry: Strontium-90 used in thickness gauges to control thickness of sheet materials • In medicine: Technetium-99m used in medical tracer diagnosis

DESCRIBE THE WAY IN WHICH THE ABOVE NAMED INDUSTRIAL AND MEDICAL RADIOISOTOPES ARE USED AND EXPLAIN THEIR USE IN TERMS OF THEIR CHEMICAL PROPERTIES Pg 41-43: Technetium-99m

• A gamma camera builds up an image based on the points from which radiation is emitted • Chemical properties of technetium-99m enable it to be combined with other compounds to study different

areas of the body o E.g. combined with tin compound, it attaches to red blood cells, whereupon blood flow can be traced. o Combined with glucose, it accumulates in parts of the body where glucose is concentrated

Strontium-90

Radiation loses energy as it passes through matter, proportional to thickness/density of the material. Strontium-90 is a beta/gamma emitter used in thickness gauges to control thickness of sheet materials.

• 9038Sr 90

39Y + 0-1e + γ

If the material is too thick, less radiation passes through to the detector, causing rollers to increase pressure on the material to reduce thickness. If material is too thin, more radiation passes through to detector, causing rollers to decrease pressure to increase material’s thickness. Strontium-90 can be used in a chemically inert form sealed in a container, enabling equipment to have a long lifetime without regular maintenance Also, the heat generated by strontium-90's radioactive decay can be converted to electricity for long-lived, portable power supplies called ‘radioisotope thermoelectric generators’. These are often used in remote locations, such as in navigational beacons, weather stations, and space vehicles. USE AVAILABLE EVIDENCE TO ANALYSE BENEFITS AND PROBLEMS ASSOCIATED WITH THE USE OF RADIOACTIVE ISOTOPES IN IDENTIFIED INDUSTRIES AND MEDICINE Benefits:

• Disinfecting and extending shelf-life of food without need for harmful chemicals to humans. This allows food to be stored longer before being consumed and allows for less wastage of spoiled foods and without harmful additives to humans in the food.

• Medical diagnosis and treatment by non-intrusive radioisotopes means patients do not have to have surgery. Radiation therapy allows patients to be treated for cancer without the need for extensive operation which may not be able to take out all the cancer and takes a long time to heal from

Strontium-90: Strontium-90 is ideal because it: • Has a long half-life of 28 years, and so won’t have to be replaced very often • Low energy emission, and so minimises radiation dose as well as ensuring that sheet absorbs most of the radiation Problems: • Highly reactive chemically (reacts with air) and so must be isolated from air Radiation can cause electrons to be removed from atoms and molecules, and can: • Affect structure of enzymes so they no longer function • Alter DNA structure, causing cancer • Alter sex cells, causing defects in offspring • People who work with radioisotopes in medicine, industry and research must take precautions, including carrying a

radiation badge, wearing face masks, or protective clothing. ================ • As strontium is chemically similar to calcium (same number of valence electrons), it may be incorporated into

bones, causing leukaemia and bone cancer • Strontium-90 decays to Yttrium-90, which is a beta emitter which a much shorter half-life of 64 hours

o Yttrium-90 poses a risk of burns to eyes and skin due to fast decay