GCSE Chemistry: Alkenes, Alcohols, Carboxylic Acids and Polymers

Organic chemistry in separate GCSE Chemistry goes well beyond crude oil. Once alkenes have been made by cracking, their double bond becomes the starting point for a family of reactions, and new functional groups — the alcohol –OH group and the carboxylic acid –COOH group — lead to esters and to polymers made in two quite different ways. This material covers that second half of the organic topic; crude oil, fractional distillation, cracking and the bromine-water test are practised in the category's crude oil material.

The quiz starts with addition reactions of alkenes: ethene with hydrogen over a nickel catalyst to give ethane, and ethene with bromine to give 1,2-dibromoethane. Alcohols follow — recognising the –OH group and naming the first four alcohols from their formulae, the gentle reaction of sodium with ethanol that releases hydrogen, the conditions for fermentation (yeast, a sugar solution, a warm temperature and no air) and the oxidation of ethanol to ethanoic acid. For carboxylic acids you name an acid from its formula and predict what you see when ethanoic acid meets sodium carbonate. An alcohol and a carboxylic acid then combine, with an acid catalyst, into an ester and water.

The final questions compare the two ways of making polymers. In addition polymerisation the C=C bond opens and nothing else is produced, so you work out the repeating unit of poly(chloroethene) from its monomer. In condensation polymerisation (Higher tier) two monomers, each with two functional groups, join and lose a small molecule such as water each time. Nature uses the same idea: amino acids join to make proteins, glucose units make starch and cellulose, and DNA is built from four different nucleotides.

The flashcards collect the functional groups, names, conditions and products to learn by heart. The oral exam lets you explain these reactions aloud to an examiner who asks one question at a time and gives short, precise feedback at the end. The printable written work contains eight longer tasks answered by hand — describing and comparing reactions, writing word and symbol equations, drawing the idea of a repeating unit in words, explaining fermentation versus hydration of ethene, and comparing addition and condensation polymers — each checked against a model answer.

The content is based on the organic chemistry section of the DfE GCSE chemistry subject content; for example, in the AQA specification the reactions of alkenes and alcohols, carboxylic acids and esters, and condensation and natural polymers are chemistry-only content.

• Describe the addition reactions of ethene with hydrogen, steam and bromine and name the products
• Recognise the –OH and –COOH functional groups and name the first four alcohols and carboxylic acids
• Describe the reactions of alcohols with sodium, their combustion and oxidation, and how ethanol is made by fermentation
• Describe the reactions of carboxylic acids with carbonates and explain why they are weak acids
• Explain how an ester is made from an alcohol and a carboxylic acid
• Work out the repeating unit of an addition polymer and explain condensation polymerisation
• Identify amino acids, glucose and nucleotides as the building blocks of natural polymers

Practice material written by Zestly, based on the DfE GCSE chemistry subject content (organic chemistry: reactions of alkenes and alcohols, synthetic and naturally occurring polymers); chemistry-only placement given as an example from the AQA GCSE Chemistry (8462) specification.