About Engineering

Core 1 summary notes 1) Fossils fuels provide both energy & raw materials such as ethylene, for production of other substances
Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum
Catalytic cracking is the process whereby high molecular weight fractions are broken down to low molecular weight ones. This process is used in petroleum refineries where crude oil is broken down to smaller alkenes and alkanes, until ethene, propene, (or both) are formed. Catalytic Cracking allows greater output of high-demand products.

Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products
Ethylene, because of the high reactivity of its double bond, can form many useful products, such as plastics (polyethylene). For example, ethene can react with water to form ethanol, with a H3PO4 catalyst at 300oC. Ethene can react with oxygen in the presence of an Ag catalyst and at 250oC, to form ethylene oxide, which is further treated with dilute acid solution to form ethylene glycol. Ethene can also react with oxygen, with a copper chloride catalyst and at 150oC, to form vinyl chloride (chloro-ethene)

Identify that ethylene serves as a monomer from which polymers are made
Ethylene is the monomer which is converted into the polymer polyethylene by the process of polymerisation (chemical reaction where many small identical molecules join together to form one large molecule).

Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water and iodine in solution
Alkanes burn in air to form CO2 and H2O, and liberate large amounts of heat in the process. Alkanes also react with (or decolourise) Cl, Br, and I, very slowly, in the presence of ultra-violet light. However without UV-light no rxn occurs. However, alkenes are much more reactive, as, when they react, their double bond opens allowing the formation of single bonds, which allow alkyl groups to be attached. Therefore, a good test to determine alkanes from alkenes is to add bromine water (HOBr) which is brown. If the solution decolourises then it is an alkene and if not it is an alkane.

Identify polyethylene as an addition polymer and explain the meaning of this term
Polyethylene is an addition polymer; that is, it forms by molecules adding together without the loss of any atoms. Basically, each double bond opens out to form single bonds with the neighbouring molecules.

Outline the steps in the production of (poly) ethene as an example of a commercially and industrially important polymer
Two processes used:
An older gas phase process, which uses high-pressure (1000 to 3000 atm), high temperatures (300oC) and’initiator’ organic peroxide). This process leads to significant chain branching (addition of alkyl groups) and therefore reduces density. Hence, this process is used for low-densitypolyethylene.
The newer process, (called the Ziegler-Natta process) uses pressures of only a few atmospheres and temperatures of about 60oC and uses a catalyst which is a mixture of titanium (III) chloride and a trialkylaluminium compound. This product is more crystalline, with less branching, hence high-density. Therefore, this process is used for high-density polyethylene.

Identify the following as commercially significant monomers (pp 15):
– Vinyl chloride
– Styrene; by both their systematic and common names

Describe the uses of the polymers made from the above monomers in terms of their properties
Polyvinyl Chloride (PVC)- rigid because the chlorine side group is larger than hydrogen. This makes it stiff and reduces flexibility. It is used for sewerage pipes, down pipes, guttering because of its strength.
Low Density Polyethylene- Has chain branching meaning that chains can’t get close to one another, so it has low density. Soft and flexible. Used for wrapping plastic (glad wrap), squeeze bottles.
High Density Polyethylene- Unbranched chains intertwine and align closely, giving it high density. Hard, tough, inflexible. Used for building materials, kitchen utensils.
Polystyrene- rigid because the benzene side group is larger than hydrogen. This makes it stiff and reduces flexibility. It is used for tool handles. But if air is blown in as it is made the polystyrene forms a foam, which is used for drink cups and packaging beads. (The air makes it soft, NOT the polymer).

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
Raw materials for making many polymers come from crude oil. There is considerable concern that the world is going to use up all of its oil resources in the next few decades. How long oil supplies will last depends on our rate of consumption. The major use of crude oil is for fuel for cars, planes and trains. There is pressure to develop alternative fuels because of the greenhouse gas problems and oil supplies decreasing. Some scientists argue that because oil supplies are going to run out we should develop alternate sources of raw materials for plastics. They see ethanol, obtained from agricultural crops, as a possible source of ethene for making polymers. Cellulose could also be a possible source of making many polymers.

Explain what is meant by a condensation polymer and describe the reaction involved when a condensation polymer is formed
Condensation polymers are polymers that form by the elimination of a small molecule (often water) when pairs of monomer molecules join together. For example, cellulose is a naturally occurring condensation polymer with the monomer unit of glucose. Glucose has the molecular formula, C6H12O6 or HO-C6H10O4-OH. When polymerisation occurs, a water molecule, between a pair of glucose molecules, is eliminated.

Describe the reaction involved when a condensation polymer is formed

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 structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass
Cellulose is a condensation polymer, which is the main component of plant material (biomass). Biomass is material produced by living organisms.

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. Unfortunately, there is no simple or efficient chemical way to break cellulose into glucose.

Use available evidence to gather, process and present data from secondary sources and analyse progress in the 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
Rayon is an artificial silk. Viscose rayon is made from regenerated cellulose normally obtained from wood pulp or cotton. Purified cellulose is treated with sodium hydroxide solution before being shredded and ‘aged’. It forms a viscose solution when it is reacted with carbon disulfide and sodium hydroxide. The solution is forced into an acid solution through holes in a spinneret. The fibres are then wound onto a spool. Other solvents such as those containing the complex ion of Copper, Cu (NH3) 4 2+, can be used to dissolve the cellulose. In this case when the solution is squirted into the acid bath, Cu2+ and NH4+ ions form and the cellulose precipitates as rayon fibres.
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

Dehydration of ethanol to ethylene is performed by using a catalyst (concentrated H2SO4). This catalyst also absorbs the water formed to stop the reaction from reversing.
Equation:

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
Water is added to ethylene and produces ethanol with the aid of a catalyst (dilute H2SO4).
Equation:

Describe and account for the many uses of ethanol as a solvent for polar and non-polar substances

Ethanol is a polar molecule:

The C-O-H end of ethanol forms a dipole called a hydrogen bond (10 times stronger than a normal polar bond). The hydrogen bond forms between two molecules that have H and F, O, N.
Ethanol dissolves other polar (e.g. glucose, amino acids, some proteins) and non-polar substances (e.g. paraffin wax) because it is polar but also has a non-polar end.

Outline the use of ethanol as a fuel and explain why it can be called a renewable resource
Equation:

Ethanol is a liquid which readily burns. It is easily transportable, and because of these properties it has been proposed as alternate form of fuel for automobiles. Petrol containing 10 to 20 % ethanol can be used in ordinary petrol engines without any modifications. Use of ethanol as a fuel would reduce consumption of non-renewable crude oil.
Ethanol is seen as a renewable resource because it is basically made from carbon dioxide, water and sunlight (via glucose, fermentation). it is seen as being neutral in regards to the greenhouse effect because the carbon dioxide it releases when it burns is as much as was used in it's synthesis, however this ignores other energy inputs when producing ethanol, such as energy for fertilizer, cultivation and distillation.
Advantages:
1. Ethanol is a renewable resource- will reduce use of non-renewable oil
2. Could reduce greenhouse gas emissions
Disadvantages:
1. Large areas of agricultural land would be needed to cultivate
2. Disposal of the large amounts of smelly waste fermentation liquors would be a problem.
3. Cost

Describe conditions under which fermentation of sugars is promoted
The condition under which fermentation of sugars is promoted is an anaerobic environment operating at about 37°C. This is the type of condition where enzymes produced by yeast can work most effectively to convert sugars from biomass into ethanol.
1. Suitable grain or fruit is mashed up with water
2. Yeast is added
3. Air is excluded
4. The mixture is kept about blood temperature (37(C)

Summarise the chemistry of the fermentation process
Enzymes (biological catalysts) in the mixture convert any starch or sucrose in the mixture into glucose, and then other enzymes convert glucose or fructose into ethanol and carbon dioxide.
Equation:

Bubbles of carbon dioxide are slowly given off. Yeast can produce ethanol contents up to about 15%. Alcohol concentrations above this level kill the yeast and stop further fermentation. To produce higher alcohol contents it is necessary to distill the liquid.

Define the molar heat of combustion of a compound and calculate the value for ethanol from first-hand data.
Molar heat of combustion is the heat liberated when one mole of the substance undergoes complete combustion with oxygen at one atmosphere of pressure, with the final products being carbon dioxide and water.
Heat of Combustion of ethanol is 1360 kJ/mol
From our experimental results in 3.3.6, the molar heat of combustion of ethanol was calculated as follows:
Molar Heat = mass × (Heat gained by container + Heat gained by water) = mass × (CH2O × ΔT + CCu × ΔT) = (4.18 × 10 + 0.38 × 10) per 0.33g = 7155.285 J g–1 = 329.143 kJ mol–1 (molar mass of ethanol is 46 grams per mole)

Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use.
Process information from secondary sources to summarise the use of ethanol as an alternative car fuel, evaluating the success of current usage.
Currently, ethanol is used directly as a fuel only in Brazil, but countries such as the United States and Canada use ethanol blended into petrol at about 10 to 12%.
The advantages of ethanol are: that is non-corrosive and leads to cleaner fuel systems; it is derived from renewable feedstock’s; 10% ethanol blends in petrol can be used without modification of engines; its ability as a polar and non-polar solvent means it can dissolve gummy deposits in engines; it combusts more fully, boosting octane rating in petrol; contributes to zero net air pollution; reduces greenhouse gases by 35 to 46%.
The disadvantages of ethanol are: that it should not be used in more than 20% blends, otherwise expensive modifications are needed; large areas of arable land must be deforested to grow crops for fermentation and distillation of ethanol. If the energy used to extract this ethanol is derived from fossil fuels, then there is no reduction in greenhouse gas emissions using biofuels.
Ethanol has been trialled successfully in Australia in limited amounts on buses in Melbourne with government support. It also has been used controversially in independent service stations.
The potential of ethanol as an alternative fuel is not great; the economic cost of modifications of engines is perhaps the greatest barrier. Moreover the cost of developing infrastructure to support the new engines is another economic barrier. Unless a commercially-viable method of converting cellulose to ethanol is found, ethanol will not be used as an alternative, but rather as an extension of petrol.

Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8
Take the alkane, subtract a hydrogen and add an OH to it.
E.g. C2H6 Ethane C2H5OH Ethanol

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.
C6H12O6(aq) → (yeast provide enzymes) → 2CH3CH2OH(aq) + 2CO2(g) + Heat
Glucose Ethanol Carbon Dioxide
Yeast was added to a conical flask with a sugar solution. It was weighed and the mass recorded. Rubber tubing and a separate test tube of limewater was added to the system to verify any effervescence of carbon dioxide gas. The equipment was left to stand in prep-room conditions and re-weighed after 48 and 72 hours.
The experiment showed a loss of mass and gain of mass in the test tube. We verified carbon dioxide gas, which was evolved, by the limewater. We showed, by a previous attempt, that the experiment is exothermic (25°C to 65°C after 48 hours) using a thermos flask and thermometer.
Inevitable loss of mass occurred during each time the experiment was weighed; trapped carbon dioxide leaked out when the tubing was disconnected each time (identified by a pop) and from the connections. However, the results were consistent with the loss of mass in the flask and the gain of mass in the test tube.
By distillation after 72 hours, we converted some of the solution into a small sample of ethanol. This, the chief product of fermentation, proved our experiment was successful. By the identification of the products and the heat, we have verified the equation empirically.

Identify data sources, choose resources and perform a first-hand investigation to determine and compare the heats of combustion of at least three liquid alkanols per gram and per mole.
The experiment was set up by a retort stand, a copper can with ~50mL of water, 3 spirit burners with 3 alkanols: ethanol, propanol and butanol. An electronic balance was used to record the mass of the empty copper can, full copper can, the mass of water (by subtraction) and the mass of ethanol with the spirit burner. The copper can was heated by the spirit burner and when the temperature had risen 10K, the final mass of the spirit burner was recorded. The mass of alkanol combusted (by subtraction) was recorded and the data substituted into the following equation:
Molar Heat = mass × (Heat gained by container + Heat gained by water) = mass × (CH2OΔT + CCuΔT) = (4.18 × 10 + 0.38 × 10) per amount of alkanol = … joules per gram = … kilojoules per mole

Our experiment yielded the following results:
Ethanol = 7155.285 J g–1 = 329.143 kJ mol–1 (Mm=46)
Propanol = 8762.237 J g–1 = 525.734 kJ mol–1 (Mm=60)
Butanol = 9140.169 J g–1 = 676.373 kJ mol–1 (Mm=74)
The risks included the flammability of the alkanols and all combustion was done in an open, well-ventilated area. However, this reduced accuracy as calorimetry needs an insulated environment.
The experiment was successful in comparing the heats of combustion. It can be seen that as the molecules increase in molecular weight, the heat of combustion also increases. This is because more reactants (in terms of atoms) form more products, yielding greater enthalpy. The result is consistent in both moles and grams.
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.
A displacement reaction is a reaction in which a metal converts the ion of another metal to the neutral atom.
Oxidation is loss of electrons. Oxidizing agent or oxidant causes oxidation to take place, itself being reduced.
Reduction is gain of electrons. Reducing agent or reductant causes reduction to take place, itself being oxidized
Oxidation-reduction reactions are also called redox or electron transfer reactions.

Identify the relationship between displacement of metal ions in solution by other metals to the relative activity of metals.
The ability of metal to lose electrons is measured on the electrochemical series. This series is useful because we can then predict which metals will react with the ions of other metals. In displacement reactions, a more reactive metal will displace the ions of a less reactive metal from solution.

Account for changes in the oxidation state of species in terms of their loss or gain of electrons.
Oxidation State rules
1. Oxygen is -2 in a molecule
2. Hydrogen is +1 in a molecule (except hydrides)
3. Simple ions have the same oxidation number as the valency
4. Complex molecules add up to give zero.
5. The oxidation number of an element is zero
Changes in oxidation state result from a loss or gain of electrons.
If given a number of equations and asked which one is a redox reaction, look for a change in valency or an element being formed or entering into a compound.

Describe and explain galvanic cells in term of oxidation/reduction reactions. Outline the construction of galvanic cells and trace the direction of electron flow.

In the school laboratory, a typical galvanic cell is made as shown in the diagram[i]. Copper and zinc electrodes are used. By displacement, based on their respective reactivities, zinc atoms will release electrons (oxidation) and become zinc ions into its solution. The electrons will follow through the wire (being conductive) and the copper electrode and be attracted to the copper ions in the solution. The copper ions become copper metal (reduction) which is deposited on the electrode. The electron flow is electrical energy. The salt bridge allows for the flow of electrons but disallows the mixing of solutions.

Define the terms anode, cathode, electrode and electrolyte to describe galvanic cells.
Anode electrode is where oxidation takes place
Cathode electrode is where reduction takes place
An electrolyte is a conductive solution (eg. KNO3(aq)).

Gather and present information on the structure and chemistry of a dry cell… and evaluate it in comparison to… [a] fuel cell in terms of: – chemistry, – cost and practicality, – impact on society, – environmental impact.
CHEMISTRY
The anode reaction of a dry cell is: Zn(s) → Zn2+(aq) + 2e–, whereas in a fuel cell, it is: H2(g) + 2OH(aq) → 2H2O(l) + 2e–.
Similarly, their cathode reactions differ;
A dry cell is: NH4+(aq) + MnO2(s) + H2O(l) + e– → Mn(OH)3(aq) + NH3(aq)
In the fuel cell it is: O2(g) + 2H2O(l) + 4e– → 4OH–(aq)
Therefore it is clearly seen that both reactions differ in reagents, reagent states and products. Also a fuel cell requires a platinum catalyst while the dry cell is a spontaneous reaction. However, both reactions are reduction-oxidation reactions.
COST AND PRACTICALITY
While the fuel cell is actually older than the dry cell in terms of development, its reaction has made it difficult to implement. The dry cell, on the other hand, has spring-boarded into popularity, and only has it lately been superseded with alkaline cells. However, its small, discreet size means it has been practical for portable consumer electronics.
The fuel cell is costly for two main reasons. Firstly, the production and storage of hydrogen as a fuel need to be taken into consideration; and since it is inflammable, packaging it will be an onerous and costly task. Packaging can also be large and bulky, negating its power-density ratio. Secondly, the economics of scale means that fuel cells are produced only by a few companies (such as International Fuel Cells), and therefore it cannot compete with other solutions such as fossil fuels. Therefore, as a solution for consumer electronics, it is not yet practical.
IMPACT ON SOCIETY
The impact on society seen by dry cells is enormous; the advent of portable consumer electronics has been spearheaded by the dry cell and the alkaline cell. Only lately has its popularity been superseded by the alkaline cell, which has greater power and less defects.
The fuel cell has been made and adopted in a few areas, but its limitations stop it from being further implemented. For example, the police station in Central Park, NYC, is powered by a 200-kilowatt phosphoric acid fuel cell (ie a fuel cell with phosphoric acid as its catalyst), because laying the park with electricity cables was not viable. It has also been adopted in cars built by Ford, GM and Daimler-Chrysler in response to California’s zero-emission laws. However, further impact is predicted to be great, replacing the use of other portable chemical batteries altogether.
ENVIRONMENTAL IMPACT
Although inexpensive as a solution, the dry cell has great environmental impact. Since the zinc casings are reactive, dry cells often leak their highly-corrosive electrolyte. Furthermore, both zinc and manganese are heavy-metals, which are not beneficial for the environment. The disposal of dry cells in landfills is not only technically illegal, but highly damaging for the environment.
Fuel cell promises a totally clean solution to energy needs: its only product is water. But the fuel cell is only clean as long as the production of hydrogen is clean. One solution is to reform hydrogen from methanol from biomass feed-stocks. Another is to electrolyse water powered by solar or wind power. As long as this is done correctly, the fuel cell is many times friendlier to the environment than the dry cell.

Distinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is unstable.
Some isotopes are unstable in nature; they will disintegrate to form other more stable elements and give out radiation as the result.
Unstable isotopes are;
*elements with large atomic number ie greater than 83
*different ratio of protons and neutrons in a element

Describe how transuranic elements are produced
Transuranic elements are elements with an atomic number above that of uranium with atomic number 92.
Some isotopes do not undergo fission (splitting the atom) when hit by neutrons. Instead they absorb the neutron and thus create new elements. They can be created by bombarding nuclei with neutrons (such as in nuclear reactors).

Describe how commercial radioisotopes are produced
Many commercially used radioisotopes are created at nuclear reactors. When the uranium nucleus breaks up into two nuclei, many different isotopes are formed. Differences in chemical properties of the elements produced can be used to chemically separate the different radioisotopes.
The high-speed neutrons emitted can be used to bombard atoms of various elements to produce useful neutron rich isotopes.

Identify instruments and processes that can be used to detect radiation.
It darkens photographic film; the Geiger-Muller Tube, when gas ionisation occurs it causes a pulse to be amplified to a speaker and a cloud chamber, if alpha particles present they leave a track which are clear and 6cm long while beta tracks are thing and wavy.

Identify one use of a named radioisotope: – in industry, – in medicine.
Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their chemical properties.

|Radioactive Isotope |Uses |Benefits |Problems |
| |Used as the ‘detector’ in |alpha-emitter, ionises air, no damage to |long half-life, thus making it emit radiation|
| |all smoke detectors. |humans; low energy gamma; long half-life |for a long time; it is made in nuclear |
|Americium-241 | |(432 years), does not need replacement. |reactors from radioactive and dangerous |
| | | |plutonium. |
| | | | |
| | | | |
| |Used to treat thyroid |Only the thyroid gland absorbs iodine, |Problems with I-131 are that normal thyroid |
| |disorders. Can used both to|aiding detection and treatment. Short |cells are killed in the process; technicians |
|Iodine-131 |detect, and treat thyroid |half-life (8 days), minimising long term |need regular blood tests to monitor exposure.|
| |cancer. |exposure to gamma rays. | |
| | | | |
| | | | |
| | | | |

Americium-241 works in smoke detectors because it ionises air, completing an electric circuit inside the detector. When there is smoke, soot, absorbing the alpha particles, breaks the circuit and raises the alarm.
Iodine-131 works to detect and treat diseases of the thyroid gland because the thyroid is the only major organ that uses iodine in the body. It uses iodine to produce the hormone thyroxin. It decays, emitting beta-rays which can be detected and levels recorded. Higher or lower readings indicate a malfunctioning thyroid. Half-Life is the time it takes for half the atoms in a radioactive material to break down to a non-radioactive element.

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