Polymers: Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Polymers revision notes

Tier note: questions and parts marked (0620 Extended, 5070 required) are in the Supplement column of the 0620 syllabus: repeat units and linkages, deducing an addition polymer from its alkene and back, condensation polymers, the differences between addition and condensation polymerisation, and proteins (11.8 outcomes 6–13). 0620 Core is 11.8 outcomes 1–5: monomers and polymers, poly(ethene) made from ethene, and the disposal and environmental problems of plastics (questions 3(a), 4 and 5, and parts of 1 and 2). 5070 has no tiers, so O Level candidates need all of it. Parts 3(c), 8(b) (hydrolysis) and 8(c) are background beyond both syllabuses.

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Section A

1. Define the terms monomer, polymer and repeat unit. (Repeat unit is 0620 Extended, 5070 required.) [3]

2. Name the polymer made from each monomer: ethene, propene, chloroethene. (Propene and chloroethene are 0620 Extended, 5070 required; Core names only poly(ethene).) [3]

Section B

3. Poly(ethene) is made from ethene.

(a) Describe what happens to the double bond during polymerisation. [2] (b) (0620 Extended, 5070 required) Draw or describe the repeat unit, explaining the two features that must be shown. [3] (c) Beyond the syllabus — not examinable, background only (“atom economy” is not a defined term in 0620/5070). Explain why no reactant mass is wasted in addition polymerisation.

4. Explain why most addition polymers are non-biodegradable, and give two environmental consequences. [4]

5. Compare three methods of disposing of waste plastic, giving one advantage and one disadvantage of each. [6]

6. (0620 Extended, 5070 required) Explain the difference between addition and condensation polymerisation, and give one example of a condensation polymer with the linkage it contains. [4]

7. (0620 Extended, 5070 required) A sample of poly(chloroethene) (PVC) has the repeat unit –[CH₂–CHCl]–.

(a) Deduce the structure of the monomer used to make this polymer, explaining your method. [3] (b) State the type of polymerisation used, and explain how you can tell from the repeat unit alone. [2]

8. Proteins and nylon both contain the same type of linkage.

(a) (0620 Extended, 5070 required) Name the linkage common to both, and name the natural monomers that join to form it in proteins. [2] (b) (Background — hydrolysis is not a 0620/5070 outcome.) Explain, with reference to hydrolysis, what this linkage breaks down into in each case. (c) Beyond the syllabus — not examinable, background only. Starch and cellulose are natural polymers of glucose. Name the linkage joining glucose units, and state the product of hydrolysing starch.

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Answers

1. Monomer — a small molecule that joins to others to form a polymer [1]. Polymer — a very long molecule made of many repeating units joined together [1]. Repeat unit — the smallest section of the chain that repeats along its length [1].

2. Poly(ethene) [1]; poly(propene) [1]; poly(chloroethene) or PVC [1].

3. (a) The C=C double bond breaks, becoming a single bond [1], leaving each carbon free to bond to the next monomer [1]. (b) –[CH₂–CH₂]– with n outside the bracket [1]; the bonds must extend through the brackets to show the chain continues [1] and there must be no double bond [1]. (c) (Background only — not examinable.) All of the atoms in the monomer end up in the polymer; there is no other product, so none of the reactant mass is wasted.

4. The chain has a backbone of strong, non-polar C–C bonds [1] that cannot be attacked by water or by the enzymes microorganisms produce [1]. Consequences: waste accumulates in landfill for hundreds of years, taking up space [1]; plastics enter rivers and oceans where animals ingest or become entangled in them [1].

5. Landfill — cheap and simple [1]; but uses up land and the plastic remains for centuries, and toxic additives may leach out [1]. Incineration — reduces volume greatly and the heat can generate electricity [1]; but produces carbon dioxide and, from PVC, toxic gases such as hydrogen chloride and dioxins [1]. Recycling — conserves crude oil as a finite raw material and reduces landfill [1]; but plastics must be sorted by type, which is labour-intensive and costly, and the recycled material is often of lower quality [1].

6. In addition polymerisation, unsaturated monomers join with no other product [1]. In condensation polymerisation, each monomer has two functional groups and a small molecule such as water is eliminated at each link [1]. Example: nylon, which contains amide linkages [1] [1]. (Or a polyester containing ester linkages.)

7. (a) Working backwards: put the double bond back between the two carbons and remove the extending bonds [1], giving CH₂=CHCl [1], chloroethene [1]. (b) Addition polymerisation [1]; the repeat unit shows only a two-carbon unit joined by single C–C bonds with no other linking group — no ester or amide link and no small molecule needed to explain how the units joined, which is the signature of addition rather than condensation [1].

8. (a) The amide (peptide) linkage, –CONH– [1]; amino acids [1]. (b) (Background only — not a 0620/5070 outcome.) Hydrolysis breaks the amide linkage back into its original monomers in both cases: in nylon this regenerates the diamine and diacid used to make it, and in protein it regenerates the amino acids that made up the chain. (c) (Background only — not examinable.) The glycosidic linkage; hydrolysing starch produces glucose.

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Where marks are usually lost

• (0620 Extended, 5070 required) Leaving the double bond in the repeat unit.
• (0620 Extended, 5070 required) Forgetting the bonds must pass through the brackets.
• Giving an advantage of recycling without acknowledging the sorting problem.
• (0620 Extended, 5070 required) Saying condensation polymers waste no reactant mass — unlike addition polymerisation, a small molecule (e.g. water) is also produced.
• (0620 Extended, 5070 required) Trying to “work backwards” from a repeat unit by simply deleting the brackets and n, without putting the double bond back in — the double bond has to be reinserted between the two carbons that were joined by single bonds in the polymer.
• (0620 Extended, 5070 required) Describing proteins as synthetic polymers, or forgetting that the same amide linkage found in nylon also holds proteins together — this is exactly why the two are compared so often.

Question 7 runs the logic of the Polymers revision notes in reverse — deducing a monomer from a given repeat unit — rather than only building a polymer forwards from its monomer, which is the direction most textbook questions default to.