AQA GCSE Chemistry Chemistry Paper 2 (Higher), 2022: Question 1

Correct Answer

To complete Figure 2, draw:

• A double covalent bond ( C=C ) between the two central carbon atoms.
• Single bonds connecting each carbon to its respective groups ( -CH₃ and -H ).

Key Knowledge

• Monomers vs Polymers: Monomers are small, unsaturated molecules (containing a C=C double bond). Polymers are long, saturated chains (containing only C-C single bonds).
• When converting a polymer repeating unit back to its monomer:
  1. Change the central single bond ( C-C ) to a double bond ( C=C ).
  2. Remove the extending single bonds on the left and right.
  3. Remove the brackets and the ' n '.

Exam Technique

Always count the bonds around each carbon atom in your final drawing. Carbon must always have exactly 4 covalent bonds. If your drawing has 3 or 5 bonds on a carbon, it is incorrect!

Common Errors

Students often lose marks by leaving the horizontal "open-ended" polymer bonds on the sides of the carbons in their monomer drawing. This is incorrect because it implies the carbon has 5 bonds.

Correct Answer

Any one from:

• Otherwise the copper produced would be impure / contaminated / a mixture.
• Otherwise the polymer insulation would burn or melt during heating, producing toxic fumes.
• Copper and poly(butene) are recycled using completely different methods.

Key Knowledge

Metals must be highly pure to conduct electricity efficiently. Even tiny amounts of impurities (like carbon from burnt plastic) significantly reduce copper's electrical conductivity, making it useless for electrical wiring.

Correct Answer

1. Heat the scrap copper wire until it melts.
2. Cast, reform, reshape, or mould the molten copper into the shape of pipes.

Exam Technique

For process questions, write chronologically. Use clear physical change terms (like melt, not just "heat up") and shaping terms (like cast, mould, or extrude).

Correct Answer

Any two from:

• Uses less energy than extracting copper from its ore.
• Conserves finite copper ores (preserves resources for the future).
• Produces less waste / reduces the amount of waste sent to landfill.
• Reduces environmental impacts (e.g., less mining, quarrying, or greenhouse gas emissions).

Common Errors

Do not mention cost! The mark scheme explicitly states to ignore references to cost. Sustainability is about environmental impact and resource conservation, not financial savings.

Correct Answer

• Name of solution added: Sodium hydroxide (solution) / NaOH
• Result: Blue precipitate / blue solid

Key Knowledge

Transition metal ions form distinctive colored precipitates with sodium hydroxide solution:

• Copper(II), Cu²⁺: Blue precipitate
• Iron(II), Fe²⁺: Green precipitate
• Iron(III), Fe³⁺: Brown precipitate

Ionic Equation: Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂(s)

Correct Answer

• Test: Add (acidified) barium chloride solution / BaCl₂ (or barium nitrate).
• Result: White precipitate / white solid

Common Errors

Never acidify with sulfuric acid! If you add sulfuric acid ( H₂SO₄ ) to acidify the solution, you are introducing sulfate ions. This will give a false-positive white precipitate even if the original sample had no sulfate ions. Use hydrochloric acid ( HCl ) instead.