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Reactions of alkenes and alcohols (chemistry only)
This chemistry-only topic links the structure of alkenes to addition reactions, then introduces alcohols and carboxylic acids using their functional groups and representative formulae.
52
Objectives
10
Flashcards
10
Questions
90 min
Study time
AqaGcseChemistryOrganic chemistry
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52 objective pages available
Structure and formulae of alkenes7 objectives
- Describe alkenes as hydrocarbons with a double carbon-carbon bond.
- State the general formula for the homologous series of alkenes as CnH2n.
- Explain that alkenes are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms.
- Recall the first four members of the homologous series of alkenes as ethene, propene, butene and pentene.
- Represent alkene molecules in displayed, structural and molecular formula forms.
- Recognise alkenes from their names or from given formulae.
- Visualise and represent 2D and 3D forms of alkene molecules. (MS 5b)
Reactions of alkenes5 objectives
- Explain that alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons.
- Explain that alkenes tend to burn in air with smoky flames because of incomplete combustion.
- Explain that alkenes react with hydrogen, water and halogens by addition across the carbon-carbon double bond.
- Describe the reactions and conditions for the addition of hydrogen, water and halogens to alkenes.
- Draw fully displayed structural formulae of the first four members of the alkenes and the products of their addition reactions with hydrogen, water, chlorine, bromine and iodine.
Alcohols13 objectives
- Describe alcohols as compounds that contain the functional group –OH.
- Recall the first four members of a homologous series of alcohols as methanol, ethanol, propanol and butanol.
- Represent alcohols in displayed, structural and molecular formula forms.
- Describe what happens when any of the first four alcohols react with sodium.
- Describe what happens when any of the first four alcohols burn in air.
- Describe what happens when any of the first four alcohols are added to water.
- Describe what happens when any of the first four alcohols react with an oxidising agent.
- Recall the main uses of these alcohols.
- Explain that aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast.
- Know the conditions used for fermentation of sugar using yeast.
- Recognise alcohols from their names or from given formulae.
- Write balanced equations for combustion reactions of alcohols.
- Investigate reactions of alcohols. (AT 2, 5, 6)
Carboxylic acids8 objectives
- Describe carboxylic acids as compounds that contain the functional group –COOH.
- Recall the first four members of a homologous series of carboxylic acids as methanoic acid, ethanoic acid, propanoic acid and butanoic acid.
- Represent carboxylic acids in displayed, structural and molecular formula forms.
- Describe what happens when any of the first four carboxylic acids react with carbonates.
- Describe what happens when any of the first four carboxylic acids dissolve in water.
- Describe what happens when any of the first four carboxylic acids react with alcohols.
- Explain why carboxylic acids are weak acids in terms of ionisation and pH. (HT only)
- Recognise carboxylic acids from their names or from given formulae.
Polymerisation and naturally occurring polymers19 objectives
- Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation.
- In addition polymerisation reactions, many small molecules (monomers) join together to form very large molecules (polymers).
- In addition polymers, the repeating unit has the same atoms as the monomer because no other molecule is formed in the reaction.
- Recognise addition polymers and monomers from diagrams and from the presence of the C=C functional group in the monomers.
- Draw diagrams to represent the formation of a polymer from a given alkene monomer.
- Relate the repeating unit to the monomer.
- Condensation polymerisation involves monomers with two functional groups.
- When these monomers react they join together, usually losing small molecules such as water, so the reactions are called condensation reactions.
- The simplest polymers are produced from two different monomers with two of the same functional groups on each monomer.
- Explain the basic principles of condensation polymerisation by reference to the functional groups in the monomers and the repeating units in the polymers. (HT only)
- Amino acids have two different functional groups in a molecule.
- Amino acids react by condensation polymerisation to produce polypeptides. (HT only)
- Glycine polymerises to produce a polypeptide. (HT only)
- Different amino acids can be combined in the same chain to produce proteins. (HT only)
- DNA is a large molecule essential for life.
- DNA encodes genetic instructions for the development and functioning of living organisms and viruses.
- Most DNA molecules are two polymer chains, made from four different monomers called nucleotides, in the form of a double helix.
- Other naturally occurring polymers important for life include proteins, starch and cellulose.
- Name the types of monomers from which these naturally occurring polymers are made.
Key terms
alkenedouble bondhomologous seriesunsaturatedmolecular formulafunctional group2D and 3D representationcombustionincomplete combustionsmoky flameaddition reaction
Exam tips
- Understand Alkene Structure: Remember to remember that alkenes are hydrocarbons characterized by a double carbon-carbon bond, which makes them unsaturated. Link the answer to Structure and formulae of alkenes, keep the formula or organic family precise, and avoid mixing alkanes, alkenes, cracking, combustion, monomers, and polymers.
- Remember the General Formula: Memorize the general formula for alkenes, CnH2n, to quickly identify their structure during the exam.
Common mistakes
- Misunderstanding Alkenes: Remember that alkenes are unsaturated hydrocarbons due to the presence of a double carbon-carbon bond, while alkanes are saturated and contain only single bonds.
- Confusing Alkene Formula: Remember that alkenes are unsaturated hydrocarbons with a double bond, which means they have two fewer hydrogen atoms than alkanes, leading to the correct formula CnH2n.
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