AQA GCSE Science CHEMISTRY Unit C1.5 Other useful substances from crude oil

• Know that fractions from the distillation of crude oil can be broken down (cracked) to make smaller molecules including unsaturated hydrocarbons such as ethene.

• Know that unsaturated hydrocarbons can be used to make polymers and ethene can be used to make ethanol.

• Know that ethanol can also be made by fermentation.

• You are expected to use your skills, knowledge and understanding to:

  • Be able 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.

    • You should be aware that crude oil is used to produce fuels and chemicals, and that it is a limited resource.

    • You should be able to evaluate information about the ways in which crude oil and its products are used.

      • Although you will probably know the names of some common polymers, these are not required knowledge, unless they are included in the subject content for this section eg poly(ethene) and poly(propene).

  • Be able to evaluate the social, economic and environmental impacts of the uses, disposal and recycling of polymers.

  • Be able to evaluate the advantages and disadvantages of making ethanol from renewable and non-renewable sources.

    • You should be able to compare the environmental impact of producing ethanol from renewable and non-renewable sources.

AQA GCSE Science CHEMISTRY Unit C1.5.1 Obtaining useful substances from crude oil

• a) Know that hydrocarbons can be cracked to produce smaller, more useful molecules.

  • Know this cracking process involves heating the hydrocarbons to vaporise them.

  • The vapours are either passed over a hot catalyst or mixed with steam and heated to a very high temperature so that thermal decomposition reactions then occur.

• b) The products of cracking include alkanes and unsaturated hydrocarbons called alkenes.

  • Know that alkenes have the general formula C_nH_2n

  • You should be able to recognise alkenes from their names or formulae, but do not need to know the names of individual alkenes, other than ethene and propene.

• c) Know and understand that unsaturated hydrocarbon molecules can be represented in the following forms: eg

  • molecular formula of propene

  • displayed formula of propene

  • You should know that in displayed structures = represents a double bond.

• d) Know and understand that alkenes react with bromine water, turning it from orange to colourless.

• e) Know that some of the products of cracking are useful as fuels.

• Revision notes: ALKENES - unsaturated hydrocarbons

• Revision notes: Cracking - a problem of supply and demand, other products from oil

AQA GCSE Science CHEMISTRY Unit C1.5.2 Polymers

• a) Know that alkenes can be used to make polymers such as poly(ethene) and poly(propene).

  • Know and understand that in these reactions, many small molecules (monomers) join together to form very large molecules (polymers). For example:

    • 

    • The polymerisation of the monomer ethene to form the polymer poly(ethene).

    • You should be able to recognise the molecules involved in these reactions in the forms shown in the subject content.

    • You should be able to represent the formation of a polymer from a given alkene monomer.

      • No further details of polymerisation are required.

• b) Know that polymers have many useful applications and new uses are being developed, for example:

  • new packaging materials, waterproof coatings for fabrics, dental polymers, wound dressings, hydrogels, smart materials (including shape memory polymers).

  • You should be able to consider the ways in which new materials are being developed and used, but will not need to recall the names of specific examples.

• c) Know that many polymers are not biodegradable, so they are not broken down by microbes and this can lead to problems with waste disposal.

  • Knowledge of specific named examples is not required, but you should be aware of the problems that are caused by landfill sites and by litter.

• d) Plastic bags are being made from polymers and cornstarch so that they break down more easily.

  • Biodegradable plastics made from cornstarch have been developed.

• Revision notes: Polymerisation - Addition Polymers

AQA GCSE Science CHEMISTRY Unit C1.5.3 Ethanol

• a) Know that ethanol can be produced by hydration of ethene with steam in the presence of a catalyst.

  • No further details of these processes are required.

• b) Know that ethanol can also be produced by fermentation with yeast, using renewable resources.

  • Know that this can be represented by: sugar ==> carbon dioxide + ethanol 

• Revision notes: Alcohols - Ethanol production

• Revise any practical work/demonstrations used to develop your skills and understanding which may include the following (which should also be revised, helps in understanding 'how science works' and context examination questions):

  • 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 the amount of water that can be absorbed by a hydrogel (eg those used as additives to garden composts),

  • testing coated fabrics for water penetration.