Production of Materials

Production of Materials2013

Contextual OutlineHumans have always exploited their natural environment for all their needs including food, clothing and shelter. As the cultural development of humans continued, they looked for a greater variety of materials to cater for their needs. The twentieth century saw an explosion in both the use of traditional materials and in the research for development of a wider range of materials to satisfy technological developments. Added to this was a reduction in availability of the traditional resources to supply the increasing world population. Chemists and chemical engineers continue to play a pivotal role in the search for new sources of traditional materials such as those from the petrochemical industry. As the fossil organic reserves dwindle, new sources of the organic chemicals presently used have to be found. In addition, chemists are continually searching for compounds to be used in the design and production of new materials to replace those that have been deemed no longer satisfactory for needs. This module increases students understanding of the implications of chemistry for society and the environment and the current issues, research and developments in chemistry.

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 identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum

Ethene is also called Ethylene. It has a double covalent bond between the carbon atoms and dispersion intermolecular forces. It is a gas at room temperature.It is most widely used as starting substance for polymers and is obtained from crude oil as bi-product or from cracking. (Cracking is the chemical process of breaking large hydrocarbons into smaller molecules.Decane(g) -> Octane(g) + Ethene(g)C10H22(g) -> C8H18(g) + C2H4(g)In the cracking process, catalysts are often used. The products can be controlled using different catalysts and different temperatures.

identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful productsAlkanes and Alkenes both readily combustCombustion of Ethene:C2H4 + 3O2 -> 2CO2 + 2H2OAlkenes are more reactive than alkanes because of the high electron density of the double bonds. Alkenes undergo addition reactions across the double bond.HydrogenationC2H4(g) + H2(g) Platinum-> C2H6(g) [Ethane](Platinum is catalyst)

HalogenationC2H4(g) + Br2(g) -> C2H4Br2 [1, 2-dibromoethane](Used to distinguish between alkanes and alkenes because of colour change)

Bromine WaterC2H4(g) + HOBr(l) -> C2H4BrOH(aq)

HydrationC2H4(g) + H2O(l) -> C2H5OH(aq) [Ethanol]

Substance FormedReactionUse

EthanediolCold dilute KMnO4Antifreeze

Ethanol+ H2O with presence of catalyst of H2SO4 Solvent + fuelMethylated Spirits

DibromoethaneAddition of BrominePetrol additive

PVCAddition polymerisationPlastic water piper and hoses

PolyethyleneAddition polymerisationBuckets, cling wrap

PolystyreneAddition polymerisationInsulation, coffee cups

identify that ethylene serves as a monomer from which polymers are madeMonomer a simple compound that joins together to form a polymerPolymer large carbon molecules made by joining monomers togetherPolymerisation is a chemical reaction in which many identical small molecules join to form one large molecule. Ethene joins to form polyethene. identify polyethylene as an addition polymer and explain the meaning of this termPolyethene is an additional polymer.An additional polymer forms when small molecules (monomer) such as ethene, add together to form long molecules (polymers), like polyethene, without the loss of any atoms. That is, no other product forms. outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer[A free radical has an unpaired outer shell electron and is very reactive]Initiation chemical called initiator starts reaction by opening the double bond of ethene, forming a free radicalPropagation the monomers join together to form a chainTermination when a free radical ethene chain combines. A complete molecule is formed and the process stopsThe resulting polymers have varied lengths.Two different polyethene can be manufactured, depending on the reaction conditions.Type of PolyetheneConditionsDescriptions/Properties

Low Density PolyetheneLDPEPeroxide with O-O bond that breaks to form free radical (initiate)High gas pressure and temperatureShort, branched chainsBranches every 6 8 carbonsLow densityWeak dispersion forcesLow MP

High Density PolyetheneHDPEZiegler-Natta catalystLow gas pressure and temperatureLong straight chainsUnbranchedStrong dispersion forcesHigh MP, dense

identify the following as commercially significant monomers: vinyl chloride styreneby both their systematic and common names describe the uses of the polymers made from the above monomers in terms of their propertiesNamePolyvinyl Chloride (chloroethene)Polystyrene (ethenylbenzene)Polyethene (ethylene)

PropertiesHard, very brittle, decomposes when heatedHard, brittle, clearLight weight, insulates when gas passed throughLDPENon-conductor, flexible, strongHDPEChemical resistant, durable, hard

Structure

UsesExternal cladding, guttering and down pipes, electrical conduit, waste water pipes, rigid panels and floor tilesCD cases, plastic drinking glasses, computer and television cabinets, StyrofoamGlad wrap, plastic bags, milk and juice containers, insulation of wires and cablesPipes, petrol containers, toys, plastic buckets, lunch boxes, freezer bags

Students: gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC course 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 processComputer AnimationDescription: the structural formulas of compounds move and combine with each other to form polymersPros: the breaking and forming of bonds are easily visible, the atoms are clearly definedCons: do not show size of the atoms, do not show how it is a 3D object, and do not show the twisting bonds

Model KitsDescription: differently coloured and sized sphere are joined together by sticks to form a moleculePros: the twisting bonds can be simulated, the model is 3D, the breaking and forming of bonds are seenCons: the atoms are not the right size, there is space inside the model2. Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuelsBiomass Mass of living matter in an area, cellulose is major component discuss the need for alternative sources of the compounds presently obtained from the petrochemical industryFinding alternative sources of hydrocarbonsForAgainst

Fossil fuel is non-renewable, finiteExpensive to find new resources

Burning fossil fuel pollutes air with greenhouse gases

Plastics made are non-biodegradable

explain what is meant by a condensation polymer describe the reaction involved when a condensation polymer is formedCondensation polymers are formed when monomers join and release a small molecule such as water. It involves the reaction between 2 functional groups. Monomers may have different functional groups on either end eg. amino acids, or sometimes consist of two different monomers. The most common functional groups are COOH (carboxylic acid), OH (alcohols) and NH2 (amines). Eg. Glucose -> cellulose, amino acids -> proteins [natural] Polyester [synthetic]Eg. when glucose forms cellulose, the 2 OH groups (hydroxyl) react to form a H2O molecule and leaving an O bond between the monomers. Amino acids form proteins. describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass

The cellulose polymer is a condensation polymer where beta glucose is the monomer. Every second glucose group is inverted. This leads to a linear molecule. The polymers are closely packed with hydrogen bonding. Cellulose is therefore strong and rigid.

There can be 10000 glucose monomers in one cellulose polymer.Cellulose is a condensation polymer and is a major component of biomass. It is the structural component of cell walls. identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw materialCellulose contains the basic carbon-chained structures needed to build petrochemicals.

For and Against Cellulose as a raw materialForAgainst

Renewable resourceTakes land and water to grow crops

Less greenhouse gas and particulate pollutionMore expensive

BiodegradableOne use only, not durable

Readily availableHarder to break down

Major component in biomassUses fossil fuel energy to produce

Can be obtained from wasteTakes time

Addition Polymerisation and Condensation PolymerisationAdditionCondensation

Double bonds break and monomers join togetherNo double bonds

No by-product formedSmall molecules like water formed as by-product

Non-polar substancePolar-substance

DispersionDipole-dipole and Hydrogen bonding

No functional groupsFunctional groups on either end of monomer

Only 1 type of monomerCan be 2 monomers joined together

Students: 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 propertiesName: Biopol The trade name of the biopolymer is Biopol. Biopol is a polyhydroxyalkanoate (PHA) and it is a co-polymer consisting of the monomers 3-hydroxybutryate (PHB) and 3-hydroxyvalerate.

Organism Used: Alcaligenes Eutrophus: It is grown in tanks with a carbon-based food source.Uses: In the food industry, it is used for disposable utensils, cups and plates as well as plastic wrap for packaging and a coating for paper and cardboard. It is also used for disposable razors, nappies, rubbish bags, shampoo and cosmetic containers.In agriculture it is used a carrier for slow release insecticides, herbicides or fertiliser. In medicine, it is used for gauzes, sutures, implants and coatings for drugs.

Properties insoluble in water but is soluble in chlorinated hydrocarbons very high melting point UV light resistant as well as being acid and base resistant Completely degradable to carbon dioxide and water when exposed to soil and rivers and other sewage Decomposes quicker when there is no oxygen so it is advantageous in landfills Biocompatible with a minimal chance of being rejected by the body Nontoxic substance Renewable resources Stable in both air and in humidity High tensile strength Permeable to oxygenRelate use to PropertyFood utensils Insoluble in water, acid and base resistant, non-toxic, high melting point. Does not react with food and is safe as it is non-toxic, safe to carry hot foods.Disposable tools degradable to CO2 and H2O, decomposes quicker w/o oxygen, nontoxic, renewable. Environmentally friendly, easily decomposes in landfills Medical suture Biocompatible, biodegradable, high tensile strength. Will not be rejected by the body or react with the body and will naturally decompose, no further surgery is needed to remove them.

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 usedDehydration is the removal of water from the alcohol. An OH group is removed from one carbon and hydrogen from another carbon and a double bond is formed. Ethanol is stable and does not spontaneously convert to ethene but will in the presence of concentrated H2SO4 (catalyst). The reaction is heated.C2H5OH(l) H2SO4-> C2H4(g) + H2O(l)

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 usedWater adds across the double bond of ethene. The catalyst used is dilute H2SO4. One of the double bond breaks, one carbon forms covalent bond with H and one carbon forms covalent bond with OH. The reaction is also heated. C2H4(g) + H2O(l) 2CO2(g) + 3H2O(g) Molar Heat of combustion: 1367kJ/molWhen ethanol is made from biomass, it is a renewable resource. When it is made from fossil fuel, it is a non-renewable resource. describe conditions under which fermentation of sugars is promoted yeast (micro-organism, enzymes) heat (35 37 degrees) No oxygen (anerobic) Water (sugar solution) Sugar source (glucose) Sulfur dioxide to kill bacteria (optional) Nutrients for yeast growth (optional) Max 15% ethanol, more than that, yeast gets killed

summarise the chemistry of the fermentation processC6H12O6(aq) Yeast(35-37)-> 2C2H5OH(l) + 2CO2(g) define the molar heat of combustion of a compound and calculate the value for ethanol from first-hand dataThe Molar Heat of Combustion of a substance is the heat released when one mole of the substance undergoes complete combustion with oxygen at standard atmospheric pressure with the final products being CO2 gas and liquid water.The molar heat of combustion is always positive even when the enthalpy change is negative (by definition). assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its useAdvantagesDisadvantages

More complete combustion, cleaner than fossil fuels Easily transportable liquid Petrol containing 10 20% ethanol can be used in normal engines Renewable resource, from waste product otherwise burnt Carbon neutral Not proved that it releases less greenhouse gas Still requires fossil fuel energy to make ethanol Large areas of agricultural land Soil erosion, deforestation, fertiliser run off, salinity Disposal of large amounts of smelly waste Lower heat of combustion therefore less energy for same amount of octane

identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8CnH2n+1OHTo names alcohols:1. Use the stem name according to the number of carbon atoms2. Remove e and replace with ol3. Note the position of the OH group receives the lowest number

Students: 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 process information from secondary sources to summarise the processes involved in the industrial production of ethanol from sugar cane

1. Processing crushing/grinding2. Filter concentrated sugar solution3. Fermentation with yeast about 3 days, 10-15% ethanol4. Distillation 95% ethanol5. Dehydration process information from secondary sources to summarise the use of ethanol as an alternative car fuel, evaluating the success of current usageEthanol was first produced by the fermentation of starches and sugars. As the demand for petrol increased with an increase of cars, crude oil fractions were catalytically cracked for more yield and the by-product was ethylene. It became more economical to produce ethanol from ethylene than sugars. In 2002, the Australian government offered large subsidies to encourage use of biofuel. Ethanol is used as a petrol additive in cars and engines. E10 is petrol with 10% ethanol. In Brazil, fuels have 25% ethanol and cars are modified to accommodate that. 40% of its fuel demand is replaced by ethanol.

The growing and processing of suitable crops, fermentation and separation are energy consuming processes and expensive, although plant waste materials can be used. As it is impossible grow enough crops to supply the whole world with ethanol, it will be unlikely that ethanol will be our total fuel for the future. It will help reduce air pollution but still produces a lot of greenhouse gases in its production. As we are running out of crude oil, ethanol might be an effective way of extending our petrol reserves. solve problems, plan and perform a first-hand investigation to carry out the fermentation of glucose and monitor mass changes present information from secondary sources by writing a balanced equation for the fermentation of glucose to ethanol 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

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 identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metalsThe activity series of metals from most reactive to least reactive is also based on the ease at which the metal loses electrons. The more active the metal, the more easily the electron is lost. This means that when the more active metal is placed in a salt solution of a less active metal, the more active metal will lose electrons and move into solution while the less active metal will gain electrons and move out of solution.A displacement reaction is a reaction in which a metal converts the ion of another metal to the neutral atom.Oxidation and ReductionRedox reactions include all reaction in which electrons are transferred from one species to another.Oxidation is Loss of electronsEg. Magnesium is oxidised to magnesium ionsMg(s) -> Mg2+ + 2e- Reduction is GainEg. Calcium ions are reduced to calciumCa2+ + 2e- -> Ca(s)Note: Oxidation and reduction must occur at the same time. You must have an electron donor and an electron acceptor.Reductant an electron donor, also called reducing agent. It loses electron.Oxidant an electron acceptor, also called an oxidising agent. It gains electron. account for changes in the oxidation state of species in terms of their loss or gain of electronsThere are limitations to this concept of oxidation-reduction because there are cases where it is difficult to determine from the equation exactly how and where electrons have been transferred. This difficulty is overcome by using oxidation state. If there has been a change in the oxidation state of a species, then an oxidation-reduction reaction has occurred.

Rules for assigning oxidation statesSubstances in the elemental state have oxidation state 0Monatomic ions, oxidation state is charge of the ionSum of oxidation state of all atoms in neutral molecule is 0Sum of oxidation states of all atoms in polyatomic ion is charge of ionSome elements have fixed oxidation states in all compoundsGroup 1 metals have oxidation state +1, Group 2 metals have oxidation state +2Combined oxygen have oxidation state -2 except peroxides(-1) and F2O (+2)Combined hydrogen have oxidation state +1 except metal hydrides (-1)Changes in the oxidation state of species can be explained in terms of their loss or gain of electrons. describe and explain galvanic cells in terms of oxidation/reduction Reactions outline the construction of galvanic cells and trace the direction of electron flow define the terms anode, cathode, electrode and electrolyte to describe galvanic cellsGalvanic Cell a device constructed so that a reductant and oxidant are physically separated, but connected by an external circuit made of a conductor and a salt bridge. A galvanic cell is composed of two half-cells, a reductant half-cell and an oxidant half-cell. This arrangement ensures that electrons cannot go directly from the reductant to the oxidant, but they will move through the external circuit.Half Cell is an electrode in a 1M solution of positive ions derived from the electrode material. Eg. Cu in CuSO4 solution.Electrode a conducting plate (usually metal) that connects the cell to the external circuit.Anode the electrode where oxidation takes place. This is the negative electrode in a galvanic cell.Cathode the electrode where reduction takes place. This is the positive electrode in a galvanic cell.Salt Bridge an electrolyte or electrolyte gel that joins two half cells in a galvanic cell and allows movement of ions to maintain a balance of charges. The salt used in the salt bridge must not react with the cation.Electrolyte a substance that conducts electricity in solution or molten stateGalvanic Cell NotationGalvanic cells are often written like this: Zn(s)|Zn(NO3)2(aq)||Cu(NO3)2(aq)|Cu(s) The redox couples are Zn|Zn2+ and Cu|Cu2+ It is conventional to write the oxidation half-cell first (anode first) || is the salt bridge The nitrate ions are spectator ions and are involved in maintaining charge balance in electrolytesA galvanic cell does not necessarily have reactive metal electrodes. Chlorine and hydrogen are bubbled over platinum electrodes which are inert.Students: 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 solutionA standard hydrogen half-cell is used to measure the standard reduction potential. 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 impactSee attached sheet solve problems and analyse information to calculate the potential requirement of named electrochemical processes using tables of standard potentials and half-equationsStandard PotentialsIt is possible to measure the voltage of electrochemical cell. To obtain reliable and reproducible results standard conditions are used. They are: Electrolyte concentration 1.0mol/L Standard Temperature 25oC Standard pressure 100kPa (if a gas)A standard half-cell is chosen for a reference. The standard half-cell potential, Eo is a quantitative measure of the electron attracting ability of an ion in its standard state in the half-cell compared to the electron attracting ability of the hydrogen atom in the standard hydrogen reference cell. (How easily will it gain electrons) If Eo is negative then the substance has less tendency to gain electrons (be reduced). If the Eo is positive then the substance has a greater tendency to be reduced than H+Standard electrode potentials are sometimes called standard redox potentials or standard reduction potentials. They are found on the back of your periodic table. Calculating the standard electron potential of EMF of the Cell1. The sign of the Eo changes if the half equation is reversed2. Balance the electrons, the electrons must cancel when the equations are added to give the overall equation3. The numerical value of Eo does not vary irrespective of what is done to balance the electrons4. Add the equations and the Eo5. If calculated Eo- Positive, then the reaction will proceed spontaneously as written- Negative, then the reaction does not occur but the reverse process occurs spontaneously

5. Nuclear chemistry provides a range of materialsIsotopes atoms of same element that contain same no. of protons but different no. of neutrons. - M is symbol of element, A is mass no., Z is atomic no.Elements are named by their mass no, eg. Chlorine-35( )A radioactive atom of an element behaves chemically exactly the same as a non-radioactive atom distinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is unstableIn stable isotope, protons and neutrons are low energy level and do not emit radioactivity.Radioactive Isotopes/radioisotopes spontaneously emit radiation from the nucleus. This process is called radioactive decay. They are unstable.Conditions of stability are related to the strength of force that hold the nuclear particles together. This is determined by the mass of atom and the ratio of the no. of protons:no. of neutrons.If atomic no. is > 83, then element is radioactiveStable light elements