9.2 Production of Materials

1 Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances

1.2.1 Construct word and balanced formulae equations of chemical reactions as they are encountered

o Thermal crackinge.g. C10H22 (l) → C8H18 (l) + C2H4 (g)

o Catalytic cracking

e.g. C10H22 (l) catalyst

→ C8H18 (l) + C2H4 (g)

o Reactions of alkanes Combustion

Complete combustion – plentiful supply of oxygen; products: water and carbon dioxidee.g. 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (l)

Incomplete combustion – insufficient supply of oxygen; products: water and carbon monoxide and/or soote.g. 2C8H18 (l) + 17O2 (g) → 16CO (g) + 18H2O (l)

2C8H18 (l) + 9O2 (g) → 16C (s) + 18H2O (l)

Substitution

e.g. CH4 (g) + Cl2 (g) UV→ CH3Cl () + HCl (aq)

o Reactions of alkenes Combustion Addition

Hydrogenationethene + hyrodgen → ethane

e.g. C2H4 (g) + H2 (g) catalyst→ C2H6

catalyst: nickel (Ni), palladium (Pd) or platinum (Pt) Halogenation

ethene +halogen → 1,2-dihaloethanee.g. C2H4 (g) + X2 → C2H4X2

X = Cl, Br, I, F... Hydrohalogenation

ethene +hydrogen halide → haloethanee.g. C2H4 (g) + HX → C2H5XX = Cl, Br, I, F...

Hydration

ethene +water dilute H 2SO4→

ethanol

e.g. C2H4 (g) + H2O (g) dilute H 2SO4→

C2H5OH (g)

Dehydration

ethanol conc .H 2SO4→

ethene +water

e.g C2H5OH (g) conc .H 2SO4→

C2H4 (g) + H2O (g)

Polymerisationo Polymer: high molecular weight material formed from

simple molecules called monomers.o Types of polymers: synthetic (e.g. polyester, nylon) and

natural (e.g. DNA, protein, cellulose)o Types of polymerisation:

Addition polymerisation Condensation polymerisation

1.2.2 Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum

1. Initiation: Free radicals are produced when the hydrocarbon chains are split into fragments at high temperatures.radical: An atom or group of atoms that has an unpaired electron very reactive

2. Propagation: Free radicals decompose to produce smaller free radicals and release ethene.

3. Termination: Free radicals react with each other to form hydrocarbon molecules.

The main products in catalytic cracking:o Lighter hydrocarbon moleculeso Ethene

Hence catalytic cracking of some fractions from the refining of crude oil is the industrial source of ethene.The catalyst used are zeolites, which are derived from volcanic rocks and is suitable for catalytic cracking due to its high thermal stability, large surface area and is non-toxic.

1.2.3 Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful productsAlkenes are more reactive than alkanes due to its reactive carbon-carbon double bond. They can undergo many addition reactions to form varying products by opening out the weaker (pi) carbon-carbon bond for other atoms (or groups of atoms) to add in.

1.2.4 Identify that ethylene serves as a monomer from which polymers are madeMonomer: the repeating component in a polymer molecule.Many monomers chemically joined together make a polymer. Ethylene is a monomer from which many different polymers are produced. The double bond opens up in the ethylene molecule which allows more ethylene radicals to add in, forming a long carbon chain.

1.2.5 Identify polyethylene as an addition polymer and explain the meaning of this term

1.2.6 Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer

1. Initiation: An initiator molecule (eg. Peroxide) is added (subjected to heat). The initiator reacts with one ethylene molecule, creating a monomer radical.

2. Propagation: The ethylene radical reacts with more ethylene monomers to increase the carbon chain and hence forming the polymer radical.

3. Termination: The polymer radicals collide and react, forming a longer chain. This is a random process, so the length of polyethylene chains can vary greatly.

1.2.7 Identify the following as commercially significant monomers:o Vinyl chlorideo Styreneby both their systematic and common names

Systematic name: Polychloroethene; monomer: ChloroetheneCommon name: Polyvinyl chloride (PVC); monomer: vinyl chlorideVinyl chloride is an ethylene molecule with one of its hydrogen atoms substituted with a chlorine atom.

Systematic name: Polyphenylethene or PolyethenylbenzeneCommon name: Polystyrene; monomer: styrene

Styrene is an ethylene molecule with one of its hydrogen atoms replaced by a benzene ring.

1.2.8 Describe the uses of the polymers made from the above monomers in terms of their propertieso Polychloroethene or Polyvinyl chloride (PVC) is used to make objects like toys, rubbish

bins, waste pipes and gutters. PVC is a hard thermoplastic, with a chlorine side chain. As chlorine is a bigger and heavier atom than hydrogen, it restricts the movement of the polymer molecules and hence decreasing its flexibility. It also has long chains with little chain branching, allowing the polymer molecules to align in orderly fashion high density crystalline polymer with high melting point and hardness due to stronger dispersion forces.

o Polystyrene is often used to make thermal cups and CD jewel cases. It is a thermoplastic with a benzene side chain. Benzene is a heavy side chain and will restrict the movement of the polymer molecules and hence decreasing its flexibility.

1.3.1 Gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC courseRefer to 1.2.1

1.3.2 Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine waterA few drops of cyclohexene were added to 2mL of bromine water in a test tube and shaken. Decolourisation of bromine water would indicate the presence of double bond and identify the chemical as an alkene.

C6H10 (l) + Br2 (aq) +H2O (l) → C6H10BrOH (l) + HBr

C6H10 (l) + Br2 (l) → C6H10Br2 (l)

The investigation was repeated with cyclohexane and all variables such as volume and temperature were held constant so that a fair comparison could be made.This investigation was carried out in a fume cabinet because bromine water is highly toxic when inhaled. Cyclohexene and cyclohexane were used because they are liquids and are easier to handle than gases. Bromine water was used because it reacts readily with a double bond but not single bonds.The reactions should be carried out in the shade to avoid the substitution reaction of an alkane.

1.3.3 Analyse information from secondary sources such as computer simulations, molecular model kits or multimedia resources to model the polymerisation process http://www.absorblearning.com/media/attachment.action?quick=zm&att=2553

2 Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels

2.3.1 Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industryPetroleum is a depleting source of energy and we must find alternative sources to cater for society’s demands. Ethene is an important starting material obtained from the catalytic cracking of heavy fractions of alkanes, as many products can be produced from this

monomer, namely polymers and plastics. Alternative sources to obtain ethene include the fermentation of starch and the decomposition of cellulose. However in today’s society, the disadvantages outweigh the advantages. The number processes required to obtain ethene are long and tedious and aren’t efficient enough to produce an economically sustainable output.

2.3.2 Explain what is meant by a condensation polymerA condensation polymer is a polymer which is produced from monomers that chemically join together by releasing water molecules. Condensation polymers can be both natural e.g. cellulose and starch, as well as synthetic e.g. polyester and nylon.

2.3.3 Describe the reaction involved when a condensation polymer is formedWhen two functional groups chemically join together from two different monomers, a small molecule e.g. water, is released.

2.3.4 Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomassCellulose is a natural condensation polymer formed from β-glucose. In the β-glucose molecule, the OH at C1 and C2 are on opposite sides of the horizontal plane.

2.3.5 Identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw materialo Cellulose is a carbon-containing condensation polymer, comprised of β-glucose

monomers. (refer to diagram above)

o Petroleum fractions have been the most convenient raw material, however, resources are finite and demand is increasing.

o Cellulose is renewable; is a major component of biomass.o Use of cellulose can be achieved in two ways:o Modify existing biopolymer chains to meet specific application, e.g. rayon.o Break down biopolymers into smaller molecules which can be used to make new

synthetic polymers.o Cellulose can be decomposed to glucose which can be used to produce ethanol via

fermentation.o Ethanol can be used as an alternate fuel or starting material for plastics production.o From ethanol, ethene can be obtained via dehydration.o However, there is no efficient method of cellulose decomposition just yet, apart from

costly thermal decomposition.2.3.1 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 propertiesBiopol – A commercially produced biopolymer

o Biopol is a trade name for polyhydroxyalkanoate.o Is made totally/majority by living organisms.o Is the co-polymer of Poly-3-hydroxybutanoate (Polyhydroxybutyrate – PHB) and

Poly-3-hydroxypentanoate (Polyhydroxventrate – PHV).o Can be produced by a number of different bacteria e.g. Alcaligenes eutrophus, as an

energy storage material.o A culture of bacteria is placed in a tank with appropriate nutrients (e.g. carbon-

based food source) so that it multiplies rapidly.o Once a large enough culture of bacteria is produced, a specific nutrient (e.g.

nitrogen) is restricted.o The bacteria stops to reproduce and instead produces the polymer as a source of

energy for later use.o This polymer is then isolated and purifiedo Properties include: insoluble in water, non-toxic, resistant to UV light, biocompatible

and biodegradable.o Biopol has a great potential for use where biodegradability is a major factor. E.g.

disposable nappies, plates, fast food utensils, shampoo bottles.o Also due its biocompatibility, biopol is used in medicine to make non-toxic and

decomposable sutures and staples.o However, biopol is more expensive to produce than petroleum based polymers.o In 1980, E coli were genetically modified to produce this polymer, which has

advantages of faster growth, higher yield and easier recovery.o The uses of transgenic plants are expected to further lower the production costs of

biopolymers.o Transgenic plants are genetically engineered plants that can be made to produce

biodegradable plastics rather than starch.

3 Other resources, such as ethanol, are readily available from renewable resources such as plants

3.2.1 Describe the dehydration of ethanol to ethylene and identify the need for a catalyst in this process and the catalyst used

Catalyst: concentrated sulfuric acid H2SO4 (aq)

3.2.2 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 use

Catalyst: dilute sulfuric acid H2SO4 (aq)

3.2.3 Describe and account for the many uses of ethanol as a solvent for polar and non-polar substancesEthanol can dissolve both polar and non-polar substances. Its polar end (hydrophilic end, containing the OH- group) is stabilised with polar molecules via dipole-dipole, ion-dipole or hydrogen bonds. The ethyl group (hydrophobic end) of ethanol establishes the dispersion force with the non-polar molecules.

3.2.4 Outline the use of ethanol as a fuel and explain why it can be called a renewable resource80% of the world’s demand for transportation fuels are petroleum derived. However, as the price of petroleum continues to rise, the concept of other fuels as alternatives becomes more attractive. Ethanol produces heat energy on combustion and therefore is regarded as a potential fuel. Ethanol is considered to a renewable resource as it can be produced via the fermentation of starches in crops, which can be regrown at a reasonably fast rate.

3.2.5 Describe conditions under which fermentation of sugars is promotedThe conditions under which fermentation is promoted are:o Presence of suitable grain or fruit mashed up with watero Presence of yeasto The exclusion of air (anaerobic environment)o The temperature is kept at about 37°C

3.2.6 Summarise the chemistry of the fermentation processo Yeast is added to mashed up grain and water.o The yeast breaks down the large carbohydrates (e.g. starch or sucrose C12H22O11 (aq)) into

simple sugars (glucose C6H12O6 (aq)).

o In an oxygen-free atmosphere, the yeast use their enzymes to break down the sugars, forming ethanol and CO2 as products.

3.2.7 Define the molar heat of combustion of a compound and calculate the value for ethanol from first-hand dataMolar heat of combustion is the amount of energy lost when a mole of a compound is combusted. The theoretical molar heat of combustion value for ethanol is 1367 kJ/mol while the experimental value is 281 kJ/mol.

3.2.8 Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use

o As a solvent (industrial, pharmaceuticals…) Can dissolve polar and non-polar substances. Polar end is stabilised with polar molecules via dipole-dipole, ion-dipole or

hydrogen bonds. Ethyl group establishes dispersion forces with non-polar molecules.

o As a potential fuel Ethanol produces heat energy on combustion and therefore is regarded as a

fuel.o Advantages:

Renewable “Greenhouse neutral” – net amount of CO2 released into atmosphere is

zero. Ethanol undergoes complete combustion more readily than octane due to

shorter carbon chain and contains oxygen in its structure cleaner fuelo Disadvantages:

Engines must be modified to run on fuel containing more than 20% ethanol Large areas of land required to grow crops that will be harvested for ethanol

production via fermentation. Soil erosion Land can be used for other purposes

Greenhouse unfriendly energy input for mechanical planting, harvesting and distillation of ethanol

Disposal of fermentation wastes presents major environmental issues.3.2.9 Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8

Number of carbons

Structure Name of alkanol

1 methanol

2 ethanol

3 propan-1-ol

4 butan-1-ol

5 pentan-1-ol

6 hexan-1-ol

7 heptan-1-ol

8 octan-1-ol

3.3.1 Process information from secondary sources such as molecular model kits, digital technologies or computer simulations to model:

o The addition of water to ethyleneo The dehydration of ethanol

Refer to 3.2.1 and 3.2.23.3.2 Process information from secondary sources to summarise the processes involved in the

industrial production of ethanol from sugar cane

3.3.3 Process information from secondary sources to summarise the use of ethanol as an alternative car fuel, evaluating the success of current usageRefer to 3.2.8

3.3.4 Solve problems, plan and perform a first-hand investigation to carry out the fermentation of glucose and monitor mass changesRefer to prac book report

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

C6H12O6 (aq) yeast→

2C2H5OH (aq) + 2CO2 (g)

3.3.6 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 moleRefer to prac book report

4 Oxidation-reduction reactions are increasingly important as a source of energy4.2.1 Explain the displacement of metals from solution in terms of transfer of electrons

The more reactive metal will displace the ions of a less reactive metal in solution. Effectively, the more reactive metal is losing electrons, while the ion is gaining electrons.

4.2.2 Identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metalsMetals that have higher oxidising potential or is a stronger reductant will displace the ions of a weaker metal in solution. Hence more active metals will displace the ions of less active metals.

4.2.3 Account for changes in the oxidation state of species in terms of their loss or gain of electronso Oxidation: loss of electronso Reduction: gain of electronso Oxidation state: a measure of a chemical species’ degree of oxidation.o Uncombined elements have an oxidation state of zero.o During displacement reactions, the oxidation states of the two metal species involved

change: Metal elements increase their oxidation state, as they lose electrons. Metal ions decrease their oxidation state, as they gain electrons.

o Oxidation states can be used to describe electron transfer in oxidation-reduction reactions:

Oxidation involves an increase in oxidation state. Reduction involves a decrease in oxidation state.

4.2.4 Describe and explain galvanic cells in terms of oxidation/reduction reactionsGalvanic cells are devices that utilises the chemical energy released by spontaneous Redox reactions to perform electrical work.Oxidation occurs at the anode (ANOX)Reduction occurs at the cathode (REDCAT)

4.2.5 Outline the construction of galvanic cells and trace the direction of electron flowA galvanic cell is comprised of two half cells, an anode half cell and cathode half cell. This arrangement ensures that electrons do not transfer directly from oxidant to reductant but rather through an external circuit. This flow of electrons can be utilised to power an electric motor or light up a light bulb. Electrons will flow from the anode to the cathode.

4.2.6 Define the terms anode, cathode, electrode and electrolyte to describe galvanic cellso Anode: where oxidation occurs; liberates electrons; negative electrode o Cathode: where reduction occurs; electron entering; positive electrodeo Electrode: a conductor used to make electrical contact in a circuito Electrolyte: solution containing free moving ions that is capable of conducting electricity.

4.3.1 Perform a first-hand investigation to identify the conditions under which a galvanic cell is producedRefer to prac book report

4.3.2 Perform a first-hand investigation and gather first-hand information to measure the difference in potential of different combinations of metals in an electrolyte solutionRefer to prac book report

4.3.3 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:

o Button cello Fuel cello Vanadium redox cello Lithium cell

o Liquid junction photovoltaic device (eg. The Gratzel cell)in terms of:

o Chemistryo Cost and practicalityo Impact on societyo Environment impact

Lead-acid cell Lithium cell

Chemistry A resilient container, usually polyethylene, holds a lead-dioxide cathode, a lead anode and a sulfuric acid electrolyte. As power is discharged from the battery, both the anode and cathode undergo a chemical reaction that progressively changes them into lead sulfate.The characteristic voltage is about 2 volts per cell, so by combining six cells you get a 12-volt battery.

A metal case holds a long spiral comprising of three thin sheets pressed together: positive electrode, negative electrode and a separator. These sheets are submerged in an organic solvent (e.g. ether) that acts as the electrolyte. The separator is a very thin sheet of micro-perforated plastic. It separates the anode and the cathode while allowing ions to pass through. The cathode is made of Lithium cobalt oxide (LiCoO2). The anode is made of carbon.When charging, lithium ions move through electrolyte from cathode to anode. During discharge, lithium ions move back to the LiCoO2 from the carbon.Each cell produces 3.7 V.Note: Lithium cell is cannot be recharged while lithium ion (Li-ion) cells can be recharged.

Cost and practicality

Low costReliableRobustCan deliver very high currentsRecyclableVery heavy and bulky

Higher voltage than normal AA alkaline battery and more compact.Rechargeable (only lithium-ion batteries)Slower discharge rate

Used in vehicles, back-up power supply longer battery lifeCompactMore expensive than alkaline batteriesUsed in phones, cameras, laptops, etc.

Impact on society

Lead acid batteries are important in today’s society to maintain smooth running operation of electricity in order to handle rapid fluctuations in the demand for electricity. They deliver large amounts of electricity to power vehicles and machinery.

With the ability to be recharged, consumers are able to minimise waste and money by essentially reusing their lithium ion batteries. It also has a longer battery life due to a slower discharge rate. This allows consumers to use their lithium battery device for longer.

Environment impact

Lead is a heavy metal (toxic) and improper disposal can be hazardous to the environment.

Classified as non-hazardous and can be recycled.However, Lithium can react with water or air to cause a fire/an explosion.

4.3.4 Solve problems and analyse information to calculate the potential requirement using tables of standard potentials and half-equationsRefer to examples in chemistry book

5 Nuclear chemistry provides a range of materials5.2.1 Distinguish between stable and radioactive isotopes and describe the conditions under

which a nucleus is unstableStable isotopes do not readily decay while radioactive isotopes are unstable and emit radiation as they spontaneously release energy and decay. The conditions under which a nucleus is unstable are:o Z>83: isotopes with too many protons are unstable

n to p ratio is outside the stability zoneo When the proton to neutron ratio is out of the stable range.

5.2.2 Describe how transuranic elements are producedTransuranic elements with atomic numbers 93 to 95 are produced in a nuclear reactor. Neutrons are bombarded at the target nuclei to make a new element.

U92238 + n0

1 → U92239

U92239 → Np93

239 + e−10

Transuranic elements with atomic numbers 96 and above are produced using particle accelerators. Small charge atomic particles (usually nuclei of He, B or C) are accelerated to very high speeds by using electrical attraction and repulsion. The small particles with high kinetic energy then hit a target of large atoms.

Pu94239 + He2

4 → Cm96242 + n0

1

Cm96242 + He2

4 → Cf98245 + n0

1

5.2.3 Describe how commercial radioisotopes are producedA particle accelerator is used to make neutron rich radioisotopes. A neutron rich isotope contains more neutrons than other atoms of the same element. Refer to 5.2.2 for the process.A cyclotron is used to make neutron deficient radioisotopes. Cyclotrons use the same acceleration of positive particles as a linear accelerator but have electromagnets so that the charge particles follow a spiral path. This makes the cyclotron compact enough to fit in a hospital basement.

5.2.4 Identify instruments and processes that can be used to detect radiationGeiger-Muller counters are used for high energy ionising radiation (strong radioactive emissions). The radiation ionises argon gas in a sealed metal tube and produces electrons and positive ions which move to oppositely charged electrodes. The small pulse of electricity produced is amplified and counted by attached electronic circuits. Ionising radiation can also be detected by changes in silver halide crystals in photographic film, discharge of electroscopes and condensation of vapour to liquid in cloud chambers.

Scintillation counters are used for low energy non-ionising radiation (weak radioactive emissions). Energy is transferred to an atom by raising an electron to an outer energy level further from the nucleus. When this excited electron drops back to a level closer to the nucleus, light is emitted. A photocell produces a pulse of electric current when hit by the light. This process is often preferred in investigating biological systems as higher energy ionising radiation would form ions which can interfere with the normal chemical reactions in cells.

5.2.6 Identify one use of a named radioisotope:o In industry

Cobalt-60 is used for detection of cracks and flaws in metal such as a in castings and welds

o In medicineTechnetium-99m is used for investigating changes in human body organs or tissues

5.2.7 Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties

o In industry Cobalt-60 is used in industrial radiography to inspect metal parts and welds

for defects. Beams of radiation are directed at the object to be checked from a sealed source of Co-60. Radiographic film on the opposite side of the source is exposed when it is struck by radiation passing through the objects being tested. More radiation will pass through if there are cracks, breaks, or

other flaws in the metal parts and will be recorded on the film. By studying the film, structural problems can be detected.

Co-60 is used because it is an emitter of gamma rays which will penetrate metal parts. Co-60 has a half-life of 5.3 years and can be used in a chemically inert form held inside a sealed container. This enables the equipment to have a long lifetime and not require regular maintenance.

o In medicine Technetium-99m (Tc-99m) is used in over half of the current nuclear

medicine procedures, such as pinpointing brain tumours. Tc-99m can be changed to a number of oxidation states. This enables production of a wide range of biologically active chemicals. The Tc-99m is attached to a biological molecule that concentrates in the organ to be investigated.

Tc-99m is used because: It has a very short half-life of 6 hours It emits low energy gamma radiation that minimises damage to

tissues but can still be detected in a person's body by a gamma ray sensitive camera

It is quickly eliminated from the body Technetium is reasonably reactive; it can be reacted to form a

compound with chemical properties that leads to concentration in the organ of interest such as the heart, liver, lungs or thyroid.

5.3.1 Process information from secondary sources to describe recent discoveries of elementsTransuranic elements with atomic numbers above 95 require high-energy particle accelerators to be produced. They began to be discovered in the 1940’s. They continued to be discovered in the next few decades. The most recent discovery is of elements 118 and 116. They were discovered by accelerating a beam of krypton-86 ions into lead-208.

5.3.2 Use available evidence to analyse benefits and problems associated with the use of radioactive isotopes in identified industries and medicine

o Benefits: Commercial radioisotopes can be used for various purposes in medicines and industry.

Irradiation of foods and γ radiation from Co-60 kills bacteria and prevents decay. The same technique is used to sterilise medical equipment e.g. bandages.

Radiation is used in medical applications to assess the functioning of the heart, brain, kidneys, thyroid and other organs of the body.

o Problems: Possible dangers of regular exposure to ionising radiation. Ionising radiation

(particularly the highly charged α) nay disrupt cellular processes, by ionising biological molecules such as DNA and proteins, forming radicals and ions, which may lead to cancer development.

Radioisotopes which become incorporated into the body are particularly dangerous, like strontium-90 which replaces calcium in bones and causes leukaemia.

As such, people who are exposed more than average, usually those who work with radioisotopes in research, medicine and industry, need a radiation

badge and protective clothing which can intercept the radiation and reduces harmful nature.