Chemistry • Year 11 • Module 1 • Lesson 11
Polymers: Structure and Properties
Lock in the core vocabulary — monomers, addition vs condensation polymerisation, key linkages and structural features — before tackling harder questions.
1. Term–definition match
The definitions below are shuffled. In the right-hand column write the matching term from this list: monomer, polymer, addition polymerisation, condensation polymerisation, cross-linking, degree of polymerisation, thermoplastic, thermosetting, ester linkage, amide linkage. 10 marks (1 each)
| # | Definition | Matching term |
|---|---|---|
| 1.1 | A small molecule that can react repeatedly to form a long chain; must contain a reactive site such as a C=C double bond or two functional groups. | |
| 1.2 | A large molecule made of many repeating units joined by covalent bonds; molecular weights typically range from thousands to millions of g mol−1. | |
| 1.3 | A type of polymerisation in which alkene monomers join through opening of a C=C double bond; no atoms are lost and no small molecule is released. | |
| 1.4 | A type of polymerisation in which bifunctional monomers react to release a small molecule (usually water) at each step, forming ester or amide linkages. | |
| 1.5 | Covalent bonds that form between adjacent polymer chains, making the material rigid, insoluble, and resistant to heating. | |
| 1.6 | The number of monomer units in a single polymer chain, represented by the subscript n. | |
| 1.7 | A polymer that softens reversibly on heating because only intermolecular forces (not covalent bonds) hold the chains together; can be remoulded and recycled. | |
| 1.8 | A polymer with covalent cross-links between chains; does not soften on heating and cannot be recycled by remelting. | |
| 1.9 | The functional-group linkage —COO— formed when a carboxyl group reacts with a hydroxyl group; characteristic of polyester polymers. | |
| 1.10 | The functional-group linkage —CONH— formed when a carboxyl group reacts with an amine group; characteristic of polyamide (nylon) polymers. |
2. True or false — with correction
Circle T or F for each statement. If the statement is false, write the corrected version on the line below it. 12 marks (1 T/F + 1 correction each)
2.1 In addition polymerisation, a small molecule such as water is released at every step. T / F
2.2 The monomer for polyethylene is ethene (CH2=CH2), which contains a C=C double bond that opens during polymerisation. T / F
2.3 Nylon is classified as an addition polymer because the monomers are joined by amide linkages without loss of any atoms. T / F
2.4 Cross-linked polymers such as vulcanised rubber are insoluble in all solvents because covalent bonds between chains cannot be broken by solvents. T / F
2.5 LDPE and HDPE are both made from the same monomer (ethene) but differ in chain structure: HDPE is highly branched while LDPE has mostly linear chains. T / F
2.6 The atom economy of addition polymerisation is 100% because every atom in the monomers is incorporated into the polymer product. T / F
3. Fill-in-the-blank paragraph
Use the word bank to complete the passage. Each word is used once. 9 marks (1 per blank)
Word bank:
addition · amide · bifunctional · C=C · condensation · cross-linking · ester · thermoplastic · water
When alkene monomers that contain a ___________ double bond react together, the double bond opens and new carbon–carbon single bonds form between adjacent monomers. This process is called ___________ polymerisation and produces no byproduct, giving 100% atom economy. By contrast, ___________ polymerisation requires ___________ monomers, each with two reactive functional groups. Each reaction step releases a small molecule; when a diol reacts with a dicarboxylic acid, the byproduct is ___________ and the linkage formed is an ___________ bond. When a diamine reacts with a dicarboxylic acid, the linkage formed is an ___________ bond. Polymers where chains are only held together by intermolecular forces are called ___________ polymers and can be remelted; polymers held together by covalent bonds between chains — a process called ___________ — cannot be softened by heating.
4. Function recall
Answer each question in 1–2 sentences using precise chemical terms. 8 marks (2 each)
4.1 What structural feature must a monomer possess for it to undergo addition polymerisation? Explain why this feature is necessary.
4.2 Why does addition polymerisation have 100% atom economy, whereas condensation polymerisation does not?
4.3 Name the two types of linkage that can form in condensation polymerisation. For each, identify the two functional groups that react to produce it.
4.4 Why does increasing the degree of polymerisation (chain length) of a polymer generally increase its melting point and tensile strength?
5. Build a concept map
Draw labelled arrows between the six terms below to show how they connect. Each arrow must carry a linking phrase (e.g. “requires”, “releases”, “produces”, “determines”). Aim for at least 6 labelled arrows. 6 marks (1 per valid labelled arrow)
Supplied terms: monomer · polymer · C=C double bond · condensation polymerisation · water byproduct · chain length.
6. Label the polymer table
Complete the table by filling in all blank cells. Each row is a different addition polymer. 10 marks (1 per correct cell)
| Polymer name | Monomer formula | Substituent group (R) | One key use | Main IMF between chains |
|---|---|---|---|---|
| Polyethylene (PE) | CH2=CH2 | —H | Dispersion | |
| CH2=CHCl | —Cl | Pipes, electrical insulation | Dipole–dipole | |
| Polystyrene (PS) | —C6H5 | Packaging, insulation foam | ||
| PTFE (Teflon) | CF2=CF2 | Non-stick cookware, bearings | Dispersion | |
| CH2=CHCH3 | —CH3 | Food containers, carpet fibre | Dispersion |
Q1 — Term–definition match
1.1 monomer • 1.2 polymer • 1.3 addition polymerisation • 1.4 condensation polymerisation • 1.5 cross-linking • 1.6 degree of polymerisation • 1.7 thermoplastic • 1.8 thermosetting • 1.9 ester linkage • 1.10 amide linkage.
Q2 — True / false with correction
2.1 False. In addition polymerisation no small molecule is released. It is condensation polymerisation that releases a small molecule (commonly water) at each step.
2.2 True.
2.3 False. Nylon is a condensation polymer. The amide linkages (—CONH—) are formed by reaction of —COOH and —NH2 groups with loss of water. Addition polymers do not produce amide or ester linkages.
2.4 True.
2.5 False. It is LDPE that is highly branched (making it flexible and low-density), while HDPE has mostly linear chains (making it rigid and high-density).
2.6 True.
Q3 — Cloze paragraph
In order: C=C / addition / condensation / bifunctional / water / ester / amide / thermoplastic / cross-linking.
Q4.1 — Monomer requirement for addition polymerisation
The monomer must contain a C=C (carbon–carbon double bond / alkene). This double bond is necessary because it opens during polymerisation: each π bond breaks and the two carbons form new single bonds to adjacent monomers, extending the chain without losing any atoms.
Q4.2 — Atom economy
Addition polymerisation has 100% atom economy because every atom in the monomers appears in the polymer product — no byproduct is formed. Condensation polymerisation releases a small molecule (e.g. H2O) at each step, so some mass is lost from the polymer chain, reducing atom economy below 100%.
Q4.3 — Condensation linkages
Ester linkage (—COO—): formed when a carboxyl group (—COOH) reacts with a hydroxyl group (—OH), releasing water. Example: PET polyester.
Amide linkage (—CONH—): formed when a carboxyl group (—COOH) reacts with an amine group (—NH2), releasing water. Example: nylon.
Q4.4 — Chain length and properties
Longer chains have greater surface area in contact with adjacent chains, which increases the total strength of intermolecular forces (dispersion, dipole–dipole, or hydrogen bonds) acting between chains. More energy is required to overcome these forces during melting (higher MP) or to break the chains apart under stress (higher tensile strength).
Q5 — Sample concept map
Award 1 mark per valid labelled arrow. Examples include:
- monomer — joins to form → polymer
- C=C double bond — is required for → addition polymerisation (implied connection to monomer)
- monomer — undergoes → condensation polymerisation
- condensation polymerisation — releases → water byproduct
- condensation polymerisation — produces → polymer
- chain length — determines strength of IMFs in → polymer
Q6 — Polymer table
Blank cells (left to right, top to bottom):
- Row 1 (PE): use — shopping bags, bottles, piping
- Row 2: polymer name — PVC (polyvinyl chloride)
- Row 3 (PS): monomer — CH2=CHC6H5 (styrene); IMF — Dispersion
- Row 4 (PTFE): substituent — —F
- Row 5: polymer name — Polypropylene (PP)