Chemistry Production of Materials Notes

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1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances 1) Construct word and balanced chemical equations of chemical reactions as they are encountered • Methane + oxygen  carbon dioxide + water • CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) 2) Identify the industrial source of ethylene from the cracking of some of the fractions from refining of petroleum Generally, demand for petrol exceeds supply produced from fractional distillation of crude oil. Thus, oil refineries increase the proportion of the desired hydrocarbon (ie ethylene) by converting lower demand fractions. This process is called catalytic cracking. Catalytic Cracking: process where high molecular weight fractions from crude oil are broken into lower molecular weight compounds. 3) Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many suitable products The two bonds of ethylene are not identical. The second bond (pi-bond) is weaker than the first bond (sigma-bond). Thus, only a small amount of energy is needed to enter the system in order to convert a double bond into a single bond. This results in ethylene’s high reactivity. 4) Identify that ethylene serves as a monomer from which polymers are made • • • Ethylene is polymerised to polyethylene High pressures produce soft, low density polyethylene, consisting of tangled chains (with molecular masses 100,000)

5) Identify polyethylene as an addition polymer and explain the meaning of the term Addition polymerisation: a process in which many identical small molecules combine to form one large molecule, with no by-products. The small molecules are called monomers, while the large molecule is called a polymer. H C C H H







In addition polymerisation, no other products are formed. 6) Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer There are two processes used to produce polyethylene: • Older gas phase process – high pressure (1000-3000atm), high temperature (300°C), initiator (organic peroxide) (1) Initiation (2) Propagation (3) Termination

7) Identify the following as commercially significant monomers – vinyl chloride, styrene – by both their systematic and common names

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Vinyl Chloride
H C H C Cl H

Systematic name: chloroethene Common name: vinyl chloride Polymer: PVC (polyvinyl chloride); polychloroethene

Properties: water-resistant, flame-resistant, flexible Uses: raincoats, guttering, flexible tubing, floor tiles Styrene Systematic name: ethenyl benzene H H Common name: styrene C C Polymer: polystyrene; poly(ethenylbenzene) H

Properties: transparent, rigid, chemically stable Uses: CD cases, food packaging, expanded form used in foam cups, and food packaging 8) Describe the uses of the polymers made from the above monomers in terms of their properties 9) Gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC course 10) Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate alkenes with the corresponding alkanes in bromine water See Prac Book (1.1) 11) analyse information from secondary sources such as computer simulations, molecular model kits or multimedia resources to model the polymerisation process 2. Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels 1) Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry The raw materials used to make petrochemical compounds such as ethylene are chiefly obtained from crude oil. The rate of crude oil consumption far outstrips the planet’s ability to convert organic matter into oil. There is a considerable concern that the world will deplete...
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