Organic chemistry
Study G2 Science Chemistry fuels, crude oil and simple alkanes and alkenes, then explain their reactions, addition polymers and plastic waste.
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Before you begin
Study G2 Science Chemistry fuels, crude oil and simple alkanes and alkenes, then explain their reactions, addition polymers and plastic waste.
Learning goals
- Name natural gas, mainly methane, and crude oil as non-renewable energy sources
- Describe crude oil as a mixture of hydrocarbons separated by fractional distillation into fractions used as fuels and as a source of chemicals
- Describe biofuels, such as bioethanol from sugarcane, as a renewable alternative to natural gas and crude oil
- Describe how biofuels are more sustainable than fossil fuels because plants take in carbon dioxide as they grow, offsetting what burning releases
- Describe a homologous series as compounds with a general formula, similar chemical properties and physical properties that change gradually as the molecules get bigger
- Describe the alkanes as a homologous series of saturated hydrocarbons with general formula CₙH₂ₙ₊₂
- Draw and name the unbranched alkanes methane to propane
- Describe the alkenes as a homologous series of unsaturated hydrocarbons with general formula CₙH₂ₙ
- Draw and name the unbranched alkenes ethene and propene
- Describe alkanes, such as methane, as generally unreactive apart from combustion and substitution by chlorine
- Describe how cracking makes alkenes and hydrogen, and why cracking is needed to meet demand for fractions of smaller molecules
- Distinguish saturated from unsaturated hydrocarbons by their structures and with aqueous bromine
- Describe the combustion, polymerisation and addition reactions with bromine and hydrogen of alkenes such as ethene
- State what polyunsaturated means on food products
- Describe how margarine is made by adding hydrogen to unsaturated vegetable oils to form a solid
- Describe polymers as large molecules built from small monomer units, with different polymers having different units
- Describe how ethene monomers form poly(ethene) by addition polymerisation
- State uses of poly(ethene) as a typical plastic, such as plastic bags and cling film
- Deduce an addition polymer's structure from its monomer, and the reverse
- Describe the pollution caused by disposing of non-biodegradable plastics
- Describe physical recycling of plastics, such as melting poly(ethene) waste into pellets
- Describe chemical recycling of plastics, such as cracking plastic waste into fuel
- Discuss the social, economic and environmental issues of recycling plastics
Syllabus statements covered
- name natural gas, mainly methane, and crude oil as non-renewable sources of energy
- describe crude oil as a mixture of hydrocarbons and its separation by fractional distillation to yield fractions which have competing uses as fuels and as a source of chemicals (see also 1.2(a))
- describe biofuel (exemplified by bioethanol from sugarcane) as a renewable alternative to natural gas and crude oil
- describe how biofuel, when compared to fossil fuels, is more environmentally sustainable in terms of the offset in carbon dioxide emission during burning by that taken in during plant growth (see also 9(e)).
- describe a homologous series as a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g. melting and boiling points; viscosity
- describe the alkanes as a homologous series of saturated hydrocarbons with the general formula CnH2n+2
- draw the structures of unbranched alkanes, C1 to C3, and name the unbranched alkanes methane to propane
- describe alkanes (exemplified by methane) as being generally unreactive except in terms of combustion and substitution by chlorine
- describe the alkenes as a homologous series of unsaturated hydrocarbons with the general formula CnH2n
- draw the structures of unbranched alkenes, C2 and C3, and name the unbranched alkenes ethene and propene
- describe the manufacture of alkenes and hydrogen by cracking hydrocarbons and recognise that cracking is essential to match the demand for fractions containing smaller molecules from the refinery process
- describe the difference between saturated and unsaturated hydrocarbons from their molecular structures and by using aqueous bromine
- describe the reactions of alkenes (exemplified by ethene) in terms of combustion, polymerisation (see also 8.3(b)) and the addition with bromine and hydrogen
- state the meaning of polyunsaturated when applied to food products
- describe the manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product.
- describe polymers as large molecules built up from small units (monomers), different polymers having different units
- describe the formation of poly(ethene) as an example of addition polymerisation of ethene as the monomer (see also 8.2(i))
- state some uses of poly(ethene) as a typical plastic, e.g. plastic bags; clingfilm
- deduce the structure of the addition polymer product from a given monomer and vice versa
- describe the pollution problems caused by the disposal of non-biodegradable plastics
- describe two methods of recycling plastics as — physical method (exemplified by melting small pieces of poly(ethene) waste into pellets)
- describe two methods of recycling plastics as — chemical method (exemplified by cracking of plastic waste into fuel)
- discuss the social, economic and environmental issues of recycling plastics.
Lessons
Work through them in order.
- Fossil fuels and crude oil fractionsExplain how crude oil is separated into fractions and why fuel and chemical uses compete.
- Biofuels and the carbon dioxide balanceCompare carbon dioxide released and taken up for bioethanol and a fossil fuel.
- Alkanes, alkenes and their structuresDraw and name the simplest alkanes and alkenes, and tell saturated from unsaturated.
- Alkane reactions and crackingDistinguish alkane reactions and use atom conservation to explain cracking products.
- Alkene reactions and the bromine testUse addition at a C=C bond to explain alkene reactions, tests and hydrogenation of oils.
- Addition polymer structures and usesConvert between an alkene monomer and its polymer's repeat unit, and explain uses of poly(ethene).
- Plastic waste and recyclingChoose a plastic-waste treatment using its material requirements, costs and environmental effects.
Practise and check
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