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IGCSE · Practice questions · Condensation polymers and proteins

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Six original Cambridge-style questions on condensation polymers and proteins (Extended).

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
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Two groups react, water leaves.

01
Recall
[2 marks]

(Extended) Name the two types of monomer used to make nylon and the type of linkage formed.

  • A dicarboxylic acid and a diamine. ✓
  • Amide linkage, –CO–NH–. ✓
02
Analysis
[2 marks]

(Extended) The monomers HOOC–□–COOH and HO–▢–OH form a polymer. Draw (or write) its repeat unit and state the type of polymer.

  • –[CO–□–CO–O–▢–O]– ✓
  • A polyester (such as PET). ✓
03
Explain
[3 marks]

(Extended) Give three differences between addition polymerisation and condensation polymerisation.

  • Addition uses alkene monomers with C=C bonds; condensation uses monomers with two functional groups. ✓
  • Addition gives only the polymer; condensation also gives a small molecule such as water. ✓
  • Addition polymers have only C–C bonds in the chain; condensation polymers have amide or ester linkages. ✓
04
Recall
[2 marks]

(Extended) Give the general structure of an amino acid and name the linkage that joins amino acids in a protein.

  • H2N–CHR–COOH (an amine group and a carboxylic acid group). ✓
  • Amide (peptide) linkage, –CO–NH–. ✓
05
Explain
[3 marks]

(Extended) A protein is heated with hydrochloric acid. Describe what happens and how the products could be identified.

  • The protein is hydrolysed: water breaks the amide links. ✓
  • The products are amino acids. ✓
  • They are separated by chromatography and made visible with a locating agent; Rf values are compared with known amino acids. ✓
06
Explain
[2 marks]

(Extended) Explain why PET is easier to recycle into new PET than many other plastics.

  • PET can be broken down (by hydrolysis) back into its monomers. ✓
  • The monomers can be purified and polymerised again to make new PET of the same quality. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.