Polymers Exam Questions

(a) A polymer is a long-chain molecule made by joining together many small molecules (monomers) [1]

(b) A monomer is a small molecule that can join with other identical molecules to form a polymer [1]

(c) Poly(ethene) / polyethylene [1]

Examiner note: The polymer name is formed by adding “poly” and placing the monomer name in brackets: ethene → poly(ethene), propene → poly(propene), chloroethene → poly(chloroethene) which is also known as PVC. The brackets distinguish the polymer from a monomer with the “poly” prefix.

(a) CH2=CHCH3 or the displayed formula showing the C=C double bond, with H on both carbons of the double bond and CH3 on one of them [1]

(b) The repeating unit shows -CH2-CH(CH3)- with the C=C broken to single bonds, brackets around the unit with n outside, and bonds extending beyond the brackets [1]

(c) Addition polymerisation [1]

(d) Any one from: rope, carpet, food containers, plastic chairs, car bumpers [1]

Examiner note: The CH3 group (methyl side chain) in propene stays attached to the same carbon in the polymer. When drawing the repeating unit, make sure the bonds extend beyond the brackets on both sides — this shows the chain continues. Missing the side chain or drawing it on the wrong carbon loses the mark.

Addition polymerisation:

• Monomers are unsaturated (contain C=C double bonds) [1]
• Only one product is formed (the polymer) / no small molecule is lost [1]

Condensation polymerisation:

• Monomers have two functional groups (e.g., -OH and -COOH, or -OH and -NH2) [1]
• A small molecule (water or HCl) is eliminated/lost each time two monomers join [1]

Examiner note: Addition polymerisation uses one type of monomer (the alkene). Condensation polymerisation typically uses two different monomers, each with two functional groups, or one monomer with two different functional groups. The loss of a small molecule in condensation is what distinguishes it from addition.

(a) CH2=CHCl showing the C=C double bond with H on one side and Cl on the other [1]

(b) Chloroethene (also known as vinyl chloride) [1]

(c) Poly(chloroethene) or PVC (polyvinyl chloride) [1]

Examiner note: To find the monomer from a repeating unit: remove the brackets, change the single bond between the two backbone carbons back to a double bond, and remove the bonds that extend beyond the brackets. This reverses the polymerisation process.

Problem 1: Most plastics are non-biodegradable — they do not decompose naturally and persist in the environment for hundreds of years, filling up landfill sites [1+1]

Problem 2: Burning/incinerating plastics releases toxic/harmful gases (such as hydrogen chloride from PVC, or carbon monoxide and carbon dioxide from other plastics), causing air pollution [1+1]

OR Problem 2: Plastic waste in oceans harms marine life — animals mistake plastic for food or become entangled [1+1]

Solution (any one): recycling plastics reduces landfill and conserves resources / developing biodegradable plastics / using less single-use plastic [1]

Examiner note: “Non-biodegradable” means bacteria and other organisms cannot break down the plastic. This is because the long carbon chains and strong covalent bonds are not recognised by decomposing enzymes. For full marks, explain the problem rather than just naming it.

(a) A diamine and a dicarboxylic acid (e.g., 1,6-diaminohexane and hexanedioic acid) [1]

(b) Water (H2O) [1]

(c) The amide linkage / peptide bond (-CONH-) [1]

(d) Any one from: strong/tough, lightweight, flexible, resistant to abrasion, can be dyed, dries quickly [1]

Examiner note: The amide linkage (-CONH-) in nylon is the same type of bond found in proteins (where it is called a peptide bond). Each time an -NH2 group reacts with a -COOH group, one molecule of water is lost. Nylon was the first fully synthetic fibre and is still one of the most widely used.

(a) -OH (hydroxyl) groups and -COOH (carboxyl) groups — one monomer is a diol (two -OH groups) and the other is a dicarboxylic acid (two -COOH groups) [1]

(b) The ester linkage (-COO-) [1]

(c) Water (H2O) [1]

Examiner note: PET (polyethylene terephthalate) is the most common polyester, used in drink bottles and polyester clothing. Like nylon, polyester is formed by condensation polymerisation with loss of water. The difference is the linkage: nylon has amide links (-CONH-), polyester has ester links (-COO-).

(a) Plastic bags, bottles, cling film, packaging [1]

(b) Rope, carpet, food containers, crates [1]

(c) Window frames, pipes, insulation for electrical cables, flooring, artificial leather [1]

Examiner note: Each polymer has specific properties that determine its use. Poly(ethene) is flexible and waterproof. Poly(propene) is strong and heat-resistant. PVC is rigid (for pipes and window frames) but can be made flexible with plasticisers (for clothing and flooring). Link the use to a property for full marks when required.