C1.5 Other useful substances from crude oil
Fractions from the distillation of crude oil can be broken down (cracked) to make smaller molecules including unsaturated hydrocarbons such as ethene. Unsaturated hydrocarbons can be used to make polymers. However, crude oil is a limited resource. Ethanol can be made from ethene or fermentation.
Candidates should use their skills, knowledge and understanding to:
■ evaluate the social and economic advantages and disadvantages of using products from crude oil as fuels or as raw materials for plastics and other chemicals
■ evaluate the social, economic and environmental impacts of the uses, disposal and recycling of polymers
■ evaluate the advantages and disadvantages of making ethanol from renewable and non-renewable sources.
Candidates should be able to compare the environmental impact of producing ethanol from renewable and non renewable sources.
Ethanol - Structure Like alkenes and alkanes, ethanol is another type of organic (carbon-based) compound. Ethanol is a two-carbon length alcohol. All alcohol molecules possess at least one C-OH group, which is known as the functional group (gives the compound its properties). Ethanol has the structural molecular formula, CH3CH2OH However, this often abbreviated to C2H5OH Combustion of ethanol Ethanol combustion (burning) produces carbon Polymers from oil - Before we start, an excellent review of this entire topic has been produced by BP Education Polymerisation Alkenes can be used to make polymers such as poly(ethene) and poly(propene). In these reactions, many small molecules (monomers) join together to form very large molecules (polymers). The polymerisation reaction occurs in the presence of a Ziegler-Natta catalyst. The polymerisation process is shown in the images, Obtaining useful substances from crude oil (cracking) - Cracking (type of thermal decomposition) Hydrocarbons can be cracked (decomposed) to produce smaller, more useful molecules. There are two types of cracking process that achieve thermal decomposition: catalytic cracking and thermal cracking. Catalytic cracking: the alkane is heated and the vapour is passed over a hot zeolite (aluminosilicate) catalyst. The reaction occurs at around 500ºC. Thermal (steam) cracking: the alkane vapour Ethanol production - Hydration of ethene Alcohols are produced industrially by hydration of alkenes in the presence of an acid catalyst. Ethanol is produced by the reaction of ethene and steam using a phosphoric acid catalyst. Fermentation Ethanol is also produced industrially by fermentation of glucose. The conditions for this process. Ethanol produced industrially by fermentation is separated by fractional distillation and can then be used as a Oil refining - Oil refining is a comprehensive simulation of the fractional distillation and uses of crude oil. The simulation is produced by Science NetLinks (AAAS)
Assessment and practical opportunities
■ demonstration of the cracking of liquid paraffin using broken pottery as the catalyst
■ testing for unsaturation in the alkenes using bromine water
■ making a polymer from cornstarch
■ demonstration of making Perspex
■ molecular modelling of polymers
■ design an investigation of a property of different plastics, eg strength, flexibility, biodegradability
■ investigate how much water that can be absorbed by a hydrogel (eg those used as additives to garden composts)
■ testing coated fabrics for water penetration.