Dot Point Notes- Production of Materials Essay Example

other free radicals to form hydrocarbon molecules.

Decane -( 2 pentyl radicals Pentyl radical ( propyl radical + ethene Propyl radical + propyl radical ( hexane Catalytic cracking is used to crack large hydrocarbon molecules into smaller ones. Heavy crude oil is heated in the presence of a catalyst composed of zeolite (aluminum silicate). The use of a catalyst allows a lower temperature (about 5000C).

Cracking is also important for producing alkenes from alkanes. e. g. decane ( ethylene +2-methyl heptane identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products Alkenes are much more reactive than alkanes because of the presence of the double bond. The double bond is a site of high electron density and molecules that have electron-attracting centers readily combine with alkenes at this point. Thus highly electronegative atoms react readily with alkenes. Alkenes often react with other molecules via an addition reaction. Common addition reactions involving ethylene include hydrogenation, halogenation and hydrohalogenation.

Hydrogenation of ethylene is the addition of hydrogen molecules across the double bond. This produces ethane. Halogenation of ethylene is the addition of halogen molecules across the double bond. The addition of chlorine to ethylene produced ethylene dichloride or 1,2 –dichloroethane – a petrol additive. Addition of bromine forms 1,2 –dibromoethane – again a petrol additive. Hydrohalogenation of ethylene involves the addition of a HX molecule where X is a halogen. The addition of HCl to ethylene produces chloroethane. The addition of HBr to ethylene produces bromoethane. These are both used as solvents and refrigerants.

Ethylene serves as a monomer from which polymers are made Polymers are long-chain molecules composed of repeating sub-units

called monomers. Polymers are sometimes called macromolecules.

Ethylene is a common monomer. The double bond of the monomer breaks to form the long polymeric chain. The nature of the polymer chain depends on the conditions of the polymerization process. Polymer chains may be linear, branched or cross-linked. HDPE (high-density polyethylene) is an example of a linear polymer with very little side-branching. Produced at relatively low temperature and pressure. Melts around 1350C. Used for buckets, milk crates, wheelie bins, freezer bags, ag pipes. LDPE (low-density polyethylene) is an example of a branched polymer with numerous side chains.

Not as strong as HDPE but more flexible because of weaker dispersion forces. More transparent than HDPE. Typically melts around 800C. Normally manufactured under high pressures. Used for garbage bags, squeeze bottles, food wrap, electrical insulation, lining for cardboard cartons.

Identify polyethylene as an addition polymer and explain the meaning of this term. The production of polyethylene involves an addition reaction across the double bond. An addition polymer forms when small molecules (the monomer), such as ethylene, add together to form long molecules (the polymer), such as polyethylene, and no other product. Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

Two different forms of polyethylene can be manufactured, depending on the reaction conditions. To produce low-density polyethylene (LDPE), a peroxide-containing an O-O the bond that breaks easily forming free radicals is used to initiate the joining of ethylene monomers. A free radical is formed when a covalent bond is broken and a bonding electron is left on each part of the broken molecule.

Ro + CH2 = CH2 ( R – CH2 – CH2

o R – CH2 – CH2 o + CH2 = CH2 (R – CH2 – CH2 – CH2 – CH2o)

And so the chain grows. Chain growth is halted by attaching hydrogens to the free radical or when two free radicals join together. The process must occur under high gas pressure (up to 3000 atmospheres) and in the range of 80 – 300oC. These production conditions result in molecules with short branches that characterize LDPE. To produce high-density polyethylene (HDPE), normal room pressures, temperatures above 300oC and catalysts made of transition metals and organometallic compounds enable the more ordered orientation of ethylene to form the long unbranched and aligned molecules in HDPE.

The catalysts are called Ziegler catalysts and consist of a compound of titanium and aluminum. Identify the following as commercially significant monomers:  vinyl chloride - styrene, by both their systematic and common names

Vinyl chloride: replacing one of the hydrogens in ethylene with chlorine gives CH2=CHCl.

This substance is vinyl chloride or, using its systematic name, chloroethene. Polymerising this substance yields polyvinylchloride (PVC). This material is thermoplastic (can be heated, re-melted and re-shaped). Additives can alter flexibility and resistance to UV rays.

The monomer is toxic. When burnt, it produces toxic and corrosive hydrogen chloride.

Styrene: replacing one of the hydrogens with a benzene ring (minus a hydrogen) gives CH2 = CH(C6H5).

This substance is known as styrene or systematically, ethenylbenzene. Polymerising this substance yields polystyrene. Polystyrene is a hard, transparent polymer. Blowing air through the polystyrene before it sets produces polystyrene foam (or Styrofoam). Describe the uses of the polymers made from the above monomers in terms of their properties.

Expanded polystyrene – white, good heat and sound packaging, plastic,

insulation properties, cups, heat insulation. Flotation devices gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC course. The following are the equations that represent the processes presented in this section of the syllabus: identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water.

This investigation requires comparison to indicate the reactivities of two substances. This is most easily achieved by direct observation of color changes when yellow bromine water is added to the two substances. The type of data is qualitative. The loss of bromine color from the bromine water will identify that reaction has occurred. This qualitative data will be valid if your plan includes the control of variables. Consider what must be kept the same in the investigation. For example, make sure that the same amount of bromine water is added and is shaken in the same way.

Use corresponding alkenes and alkanes that have similar structures preferably differing only by the presence and absence of a carbon to carbon double bond. Cyclohexene and cyclohexane are suitable to use. When performing the investigation, ensure that correct safety procedures are used and that quantities of chemicals are kept to the minimum level to observe an effect.

Analyse information from secondary sources such as computer simulations, molecular model kits or multimedia resources to model the polymerization process You can simulate and then analyze the polymerization process by using a molecular model kit to construct a model of a long chain polymer from a number of monomers, such as ethylene. Begin with at least five

separate models of the monomer. Initiate the production of the polymer by changing the C=C double bonds of two monomer models to C-C single bonds. Join the two reactive molecules with one of the single bonds (electron pairs) released when a double bond changed to a single bond. Continue this process to join the remaining monomers. You will end up with a long chain like the following.

Remember that this simulation is a micro-view of a process that is repeated over and over in the macro-production of a polymer. The many long chains produced are held together by intermolecular forces or tangling of chains.

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 Petrochemicals is chemicals made from compounds in petroleum or natural gas. They are non-renewable. Currently, Australia has petroleum reserves that will last about ten years and natural gas reserves that will last about one hundred years. Fossil fuels have taken hundreds of millions of years to accumulate.

Over 95% of fossil fuel is burnt as a source of energy and once burnt, fossil fuels are no longer available. Petrochemicals (or at least the products produced from them) are also pollutants. Plastics are essentially non-bio-degradable. This decomposition problem increases the number and size of landfills, contributing to environmental destruction. If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are used up. The most likely candidate right now is the obtaining of ethanol from plants. This ethanol can be converted into ethene. Presently

this process is less efficient than making ethene from crude oil. explain what is meant by a condensation polymer

A condensation polymer is a polymer that forms by the elimination of a small molecule (often water) when pairs of monomer molecules join together, and the functional groups are linked together. For example, when two glucose monomer molecules react through two hydroxy groups -OH, an H-OH molecule 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. describe the reaction involved when a condensation polymer has formed. The reaction involved is a condensation reaction – a reaction in which two molecules combine together with the elimination of a smaller molecule. The reaction can go on and on just like addition polymerization.

Cellulose can be up to 15000 monomer units long. Different types of links that form between monomers can be given different names. The link between an amide group and a carboxyl group is called an amide or peptide link in biochemical contexts. Condensation polymers include nylon, polyester and PET (polyethylene terephthalate) describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass Cellulose is a flat, straight and rigid molecule. It is a naturally occurring condensation polymer formed by monomer units of glucose.

The OH – is the functional groups and they join together to form the links s well as release water. Hydrogen bonding makes cellulose very strong. It is a biopolymer (polymer made from either totally or partially from

living organisms). For the binding to occur, alternate glucose units must be inverted. The bonding produces a very linear molecule because of the geometry of the rings and the C – O – C bond angles. The bulky -CH2OH groups, represented above as LOH , are on alternate sides of adjoining glucose units. Many of the hydroxy groups form hydrogen bonds that hold the cellulose chains together. The hydrogen bonding results in long strong cellulose fibers. This accounts for why wood is a strong building material.

The reduced availability of hydroxy 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. Most dry plant material consists of up to 50% cellulose. identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material Each glucose unit of cellulose has four carbon atoms joined together in a chain, so it could be regarded as a basic structure for making starting molecules for petrochemicals – molecules such as ethene (2 C atoms), propene (3 C atoms) and butene (4 C atoms).

Many current polymers are made using three-carbon monomers (such as polypropylene in Australian 'paper' currency) or four carbon monomers (such as those used to make synthetic rubbers). Unfortunately, there is no simple way of breaking cellulose into glucose and this has been the stumbling block to using cellulose as a raw material for chemicals. There is currently a significant scientific effort in finding ways of making use of cellulose. The advantages biopolymers provide include biodegradability and renewability. Their biodegradability is due to the fact that

many bacteria and fungi decompose cellulose into glucose and then eventually into carbon dioxide and water. use available evidence to gather and present data from secondary sources and analyze progress in the recent development and use of a named biopolymer.

This analysis should name the specific enzyme(s) used or organism used to synthesize the material and an evaluation of the use or potential use of the polymer produced related to its properties A biopolymer is a naturally occurring polymer generated using natural resources like plants and micro-organisms. Research has involved making polymers with living organisms. These polymers have properties similar to petrochemical-based plastics. Polyhydroxybutyrate (PHB) is one such polymer and has properties not too different from polyethylene. It was discovered some 80 years ago that PHB can be made by certain bacteria. In recent years the Monsanto company has used GE to transfer the genes for PHB production into corn plants.

The corn is grown, harvested and eaten as usual while the stalks and leaves are harvested for their PHB content. The main advantage is that PHB is biodegradable but that also limits its use (it can rot and disintegrate during use). It has properties that make it suitable to replace some plastics for packaging but it can become brittle. Two main disadvantages are that there is some resistance by farmers and consumers regarding the use of GM plants and the production of PHB is still not as cheap as using petrochemical plastics. The 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.

The following information addresses the above two syllabus points together. Ethylene and ethanol are easily interchanged by the addition of water (hydration) and the removal of water (dehydration). Catalysts such as sulfuric acid, phosphoric acid or heated ceramic solids can be used to catalyze these dehydration and hydration reactions.  Countries are rich in petroleum or natural gas, e. g. around the Persian Gulf, or petroleum refining and cracking facilities, e. g. Singapore can make ethanol by hydration of ethylene. Countries are rich in land and climate suitable for growing crops that could be used to produce ethanol, e. g.

Brazil can make ethylene by dehydration of ethanol. escribe 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. Refer to above dot point. describe and account for the many uses of ethanol as a solvent for polar and non-polar substances Ethanol is used as a solvent in dissolving medicines and food flavorings and colorings that do not dissolve easily in water. Once the non-polar material is dissolved in the ethanol, water can be added to prepare a solution that is mostly water. The ethanol molecule has a water-loving (hydrophilic) -OH group that helps it dissolve polar molecules and ionic substances. This occurs through hydrogen bonding, dipole-dipole attraction or ion-dipole attraction.

The short, water-fearing (hydrophobic) hydrocarbon chain CH3CH2- can attract non-polar molecules. The non-polar component of an ethanol molecule bonds to non-polar molecules through dispersion forces. Thus ethanol can dissolve both polar and non-polar substances. Industrially and in consumer products, ethanol is the second most important solvent after water. Ethanol is the

least toxic of all the alcohols as it is poisonous in moderate amounts rather than small amounts. Consumer products listed as containing alcohol practically always contain ethanol as the alcohol. outline the use of ethanol as a fuel and explain why it can be called a renewable resource

Ethanol combusts in the air, releasing carbon dioxide, water and heat. Because the ethanol molecule contains an O atom, the combustion is practically always complete. There is hardly any formation of the polluting CO or C forms, which form from the incomplete combustion of many other hydrocarbons. When the oxygen supply in a Bunsen burner is adequate for complete combustion, you get a hotter, colorless, almost invisible flame, like the flame of burning ethanol. In contrast, when you reduce the oxygen supply to a Bunsen flame, you get a yellow smoky flame, due to carbon. The presence of an oxygen atom in ethanol minimizes the formation of carbon in an ethanol flame.

Ethanol can be called a renewable resource because ethanol can be made from the plant material and the products of its combustion, carbon dioxide and water, are the reactants needed by plants for photosynthesis. describe conditions under which fermentation of sugars is promoted The conditions that promote the fermentation of sugar are: o a suitable micro-organism such as yeast o water o a suitable temperature for the fermenting yeast o low oxygen concentrations favoring the fermenting yeast o a small number of yeast nutrients such as phosphate salt.

Once the ethanol concentration reaches 14-15% by volume, the yeast cannot survive, and the fermentation process stops. summarise the chemistry of the fermentation process Cane sugar waste, such as molasses,

is rich in sucrose (C12H22O11), however, it is uneconomic to separate. If water and yeast is added, the sucrose reacts with water producing glucose and fructose, both of which have the molecular formula C6H12O6. Fermentation can then occur: define the molar heat of combustion of a compound and calculate the value for ethanol from first-hand data The molar heat of combustion is the heat change when one mole of the substance is combusted to form products in their standard states (that is, solid, liquid or gas) at 105 Pa (100 kPa) and 25oC (298K).

To calculate the value for ethanol from first-hand data:

1. Write a balanced equation for the complete combustion of ethanol including states of matter required for the molar heat of combustion definition.
2. Use your measurement of heat released per gram for ethanol as your first-hand data to calculate the molar heat of combustion for ethanol.
3. Compare your calculated value with a published value from a text or data book. Explain any difference in measured value and published value by considering how you carried out the measurement.

Weighing of the burner before and after use, gives a difference equal to the mass of ethanol that burned. The student does a calculation (H = –mCT) to find the amount of heat released. From these two measurements, the heat released per gram and then per mole is calculated. assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use Ethanol can be used in internal combustion engines if it can be economically produced from renewable resources or subsidized as a fuel to reduce air pollution. The advantages of using ethanol

include its complete combustion with minimal pollution. It can also be made in a number of ways.

The disadvantages of using ethanol include the need to modify fuel lines and even the engine if the ethanol is more than 10-15% when mixed with petrol. Another disadvantage is the low price of still readily available petroleum. Large tracts of land would need to be allocated to growing plants to use in the production of ethanol rather than food. Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8 IUPAC nomenclature for alkanols refers to the International Union of Pure and Applied Chemists (IUPAC) way of naming alkanols. You are only required to deal with straight-chained alkanols with up to, and including 8 carbon atoms.

Transuranic elements (aka. transuranic) are elements that come after element 92 (Uranium) on the periodic table. These elements are not found in nature and are made in the laboratory and in nuclear reactors. Twenty-two transuranic elements have been made. Protons are shot into the nucleus of atoms. This increases the atomic number and changes the element. All transuranic elements are radioactive isotopes.

Only three of the transuranic elements, those with atomic numbers 93, 94 and 95, have been produced in nuclear reactors. When U-238 is bombarded with neutrons it can be converted to U-239 that undergoes beta decays to produce neptunium and plutonium. Pu-239 is changed to americium by neutron bombardment. 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. Radioactive isotopes are either produced in a particle accelerator (e. g. cyclotron) by firing charged particles (e.g. protons or small nuclei) at high speeds at nuclei, producing a nuclear reaction that creates a radioisotope, or they are produced in a nuclear reactor, where neutrons are bombarded into nuclei. This changes the number or protons or neutrons in the nucleus, thus making it a radioactive isotope. Identify instruments and processes that can be used to detect radiation Geiger-Muller tube – It works through a sealed tube that contains argon gas. When radiation enters the tube it ionizes the gas and this creates an electric signal. This is converted into sound and amplified and this allows you to hear a tone when a particle is detected. Electroscope detects ionizing alpha particles in the air. As gamma rays have the poor ionizing ability this device does not recognize the gamma rays.

Scintillation counter - low energy radiation that is too weak to ionize atoms is called non-ionizing radiation and can be detected by a scintillation counter. Scientists investigating reactions in living things often prefer to use non-ionizing radioisotopes because ionization could cause unwanted chemical changes in living things. The non-ionizing radiation emitted transfers energy to a solvent molecule and then to a fluorescent molecule that emits light. A photomultiplier produces an amplified electrical pulse from the light. A counter counts the pulses. Identify one use of a named radioisotope in industry Am-241 is used in fire alarms.

Cobalt-60 (Co-60) is used in a process called industrial radiography, to inspect metal parts and welds for defects. In medicine, Tc-99m is used as a tracer to diagnose diseases by

showing up cancerous growths. Describe the way in which the above-named industrial and medical radioisotopes are used and explain their use in terms of their chemical properties Americium-241 is used in smoke detectors, which are used industrially as a safety measure in factories. Fire Alarms contain Am-241 which radioactively decays producing alpha particles. When no smoke is present, the alpha particles emitted from the Am ionize nitrogen and oxygen in the air in the detector.

However, when smoke is present, it absorbs the alpha particles so the rate of ionization drops and this sets off the alarm. 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 that will penetrate metal parts. Co-60 has a half-life of 5 years and can be used in a chemically inert form held inside a sealed container. This enables the equipment to have a long life and not require regular maintenance. Tc-99m (Metastable Technetium-99) is a radioisotope used in medicine as a tracer to detect abnormal cell growths (ie. cancer) and blood flow abnormalities. It is injected into the patient’s bloodstream and is observed by the gamma radiation that it emits. Tc-99m is

used because it: has a short half-life of 6 hours, is easily excreted, emits low-energy gamma radiation, shows blood flow abnormalities, is easily attached to biological carriers process information from secondary sources to describe recent discoveries of elements

In nuclear reactors, protons are fired at high speeds at atoms to change the structure and thus make new elements. The claim to production of element 118 has been withdrawn by the originating laboratory like no other laboratory anywhere in the world has been able to replicate this production. Use available evidence to analyze benefits and problems associated with the use of radioactive isotopes in identified industries and medicine. The alternative to gamma sources, X-rays, are not as penetrating and require high voltage equipment that uses a lot of electrical energy. However, the more expensive X-ray equipment is more easily disposed of and does need to be locked away in secure locations like potentially harmful gamma-ray sources.