HSC Chemistry - Production of Materials (MAJOR DOTPOINTS)

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1 HSC Chemistry Year 2015 Mark Pages 21 Published Dec 17, 2016 HSC Chemistry - Production of Materials (MAJOR DOTPOINTS) By Maalavan (97.8 ATAR)

2 Powered by TCPDF ( Your notes author, Maalavan. Maalavan achieved an ATAR of 97.8 in 2016 while attending Girraween High School Currently studying B. Commerce/B. Engineering (As of 17/12/16) at The University of New South Wales Achievements: Accelerated & Band 6 in HSC Chemistry (2015) Band 6 in HSC Economics (2016) Band 6 in HSC Physics (2016) Band E4 in HSC Mathematics Extension 1 (2016) Maalavan says: Throughout year 12 (2015/16), I was committed to achieving my best results, so I decided to work often throughout the year on achieving well in various school assessments as well as my final HSC exams. This led to me achieving great results in my HSC and achieving an ATAR that got me guaranteed entry to my first preference at UNSW by quite a large margin. Alongside my band 6s in Chemistry, Physics and Economics, I managed to score 90+ raw in my trial Chemistry and Economics papers. Aside from watching heaps of TV shows and some sport, I am interested in knowledge of business and science.

3 Maalavan Aravindan HSC CHEMISTRY NOTES: PRODUCTION OF MATERIALS 1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum Petroleum is a complex mixture of hydrocarbons, consisting mainly of alkanes as well as small quantities such of other hydrocarbons such as alkenes. Petroleum is also known as crude oil. Crude oil is notably separated into fractions of different carbon-chain length through fractional distillation, based on the various boiling points of each of these hydrocarbons. However, there is a significantly high demand for small molecular weight hydrocarbons such as ethylene in the petrochemical industry, more than can be met by supply from fractional distillation alone. Ethylene is in very high demand but is found in very small quantities after fractional distillation. In order to cater for excess demand, large hydrocarbon chains are broken into smaller hydrocarbon chains, known as cracking. Catalytic Cracking Catalytic cracking is the process of breaking down a large hydrocarbon chain into a smaller alkane and smaller alkene using catalysts called zeolites. C10H22(l) (Zeolite) C8H18(l) + C2H4(g) Conditions: 500 C, absence of air, just above atmospheric pressure, catalyst - zeolite. A zeolite is a crystalline aluminosilicate with high surface area. The cracking hydrocarbon sits (adsorbs) on the surface of the zeolite, allowing the reaction to be conducted at lower temperatures. Thermal Cracking Thermal or steam cracking is the process where a large mixture of alkanes are mixed with steam and passed through very hot metal tubes to decompose the alkanes completely into small alkenes such as ethylene, propene and butene. Some hydrogen may also be produced. C11H24(l) 4C2H4(g) + C3H6(g) + H2(g) Conditions: C, just above atmospheric pressure.

4 Identify that that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products Maalavan Aravindan Ethylene is a very reactive molecule. This is due to its unsaturated double bond, a site of high electron density. It is due to the presence of the double bond that ethylene can be transformed into a wide variety of products. Addition Reactions Addition reactions occur where a double or triple bond 'opens' and atoms/molecules are added across the bond. Examples of addition reactions: o Hydrogenation: Hydrogen gas can react with ethylene to produce ethane. o Halogenation: Reactive molecules such as Br2 can react with ethylene to produce molecules such as 1, 2-dibromoethane. o Hydration: Water can react with ethylene to produce ethanol. o Hydrohalogenation: A hydrogen halide such as HCl can react with ethylene to produce haloalkanes such as chloroethane. Other Reactions with Ethylene Oxidation reaction: Ethylene can be oxidised to produce ethylene oxide, which is reacted with acidified water to produce 1,2-ethanediol or known as ethylene glycol. Substitution reaction: Chlorine gas and oxygen can react with ethylene to produce chloroethene or known as vinyl chloride, as well as water.

5 Maalavan Aravindan In addition, ethylene is used in the production of polymers such as polyethylene. It is also used as a plant hormone to control ripening and colour development as well as in anaesthetic mixtures. Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer LDPE (Low-density polyethylene) Conditions: 300 C, atmospheres, initiator (organic peroxide). Occurs in a three step process: 1. Initiation: The organic peroxide (usually benzoyl peroxide) is thermally decomposed, producing two peroxide radicals: These radicals then cause the double bond of an ethylene molecule to open, forming activated monomers: 2. Propagation: The activated monomers react with more ethylene monomers (which increases the length of the polymer chain): 3. Termination: The polymerisation process terminates when two activated polymer chains collide. The free radicals combine, forming a non-activated polymer chain: The resulting polymer chains (LDPE) from this process have significant chain-branching and thus cannot be packed together tightly, resulting in its low density, hence the name. HDPE (High-density polyethylene) Conditions: 60 C, a few atmospheres, catalyst - Ziegler-Natta catalyst. Ziegler-Natta catalyst, consisting of a mixture of titanium (III) chloride and a trialkylaluminium compound (eg. triethyl aluminium chloride), is used for this process. Metallocene catalysts, however, are slowly replacing Ziegler Natta catalysts as they provide greater control of the polymerisation process, improving quality of the polymer product. The resulting polymer chains (HDPE) from this process are unbranched and thus can be packed together densely, resulting in its high density, hence the name.

6 Maalavan Aravindan Describe the uses of the polymers made from the above monomers (ethylene, vinyl chloride, styrene) in terms of their properties LDPE Plastic bags and cling wrap: This is due to LDPE's low density as a result of extensive side branching, which results in low dispersion forces, thus increasing flexibility. In addition, LDPE is insoluble in water, as its structure is non-polar and often large. Soft toys (rubber ducks): This is due to LDPE's low density as a result of extensive side branching, resulting in a lightweight structure and low dispersion forces, thus increasing flexibility. HDPE Cooking utensils (spatulas): This is due to HDPE's high density as a result of its crystalline, unbranched structure, resulting in greater dispersion forces, thus being hard and having a high melting point. 'Wheelie' bins: This is due to HDPE's high density as a result of its crystalline, unbranched structure, resulting in greater dispersion forces, thus having strong hardness and rigidity. PVC Water pipes: This is due to large chlorine atoms present in the structure of PVC, which prevents movement of the polymer chains and also increases dispersion forces, leading to strong rigidity and hardness. In addition, PVC is insoluble in water, as its structure is non-polar and often large. Raincoats: This is due to PVC's insolubility in water as a result of its large, non-polar structure. The use of plasticisers can increase PVC's flexibility, thus allowing for such use. Polystyrene CD cases: This is due to the presence of very large benzene rings in polystyrene's structure, which prevents movement of the polymer chains and also greatly increases dispersion forces, leading to strong rigidity and hardness. Styrofoam cups: Expanded polystyrene (or known as styrofoam) is produced through blowing gases through molten polystyrene and allowing it to cool, forming a material that is lightweight, has heat insulation and has high buoyancy. In addition, polystyrene is insoluble in water, as its structure is non-polar and often large.

7 Powered by TCPDF ( Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water Maalavan Aravindan A first-hand investigation was conducted to compare the reactivities of an alkane and its respective alkene using bromine water. Bromine water, a very reactive solution due to bromine's very high reactivity, was used as the dependent variable for the experiment. Bromine water is also used because it is naturally of yellow colour. Ethylene and ethane cannot be used as they are both gases. Instead cyclohexane and cyclohexene, two very stable liquids, were used in the experiment. METHOD: drops of bromine water were added to two test tubes, one containing approximately 5mL of cyclohexane and the other containing approximately 5mL of cyclohexene. A stopper/bung was attached and observations were recorded. The experiment found cyclohexane not to discolour the yellow bromine water. The mixture was also brought under UV light/sunlight, which resulted in very slow reactions, probably due to substitution reactions of the hydrogens with bromine. The low reactivity of alkanes in bromine water is due to the saturation of the C-H bonds, resulting in a more stable structure. The experiment then found cyclohexane to discolour the yellow bromine water. This is due to cyclohexane's unsaturated, reactive double bond, resulting in its higher reactivity. The bromine water is then able to 'open up' the double bond and add to the compound; thus an addition reaction. SAFETY: o The bromine water and hydrocarbons used in this experiment are both toxic chemicals. Bromine water is also a corrosive chemical. The hydrocarbons used in this experiment are also toxic. Avoid contact and ingestion of chemicals as much as possible. Wash skin with cold water if contact occurs with chemicals. Use a fume cupboard or otherwise have a well ventilated laboratory. Take fresh air breaks if headaches occur. o The hydrocarbons used in this experiment are non-polar and thus insoluble in water. The hydrocarbons cannot be broken down naturally. This causes an environmental problem to all life and hence all hydrocarbons should be collected in special waste containers and not wasted down the drain. These chemicals can then be processed off for decomposition. FIRST SECTION ONLY - OTHER SECTIONS IN FULL COPY