AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Higher), 2023: Question 7

✅ Correct answer (1/1)

Fullerenes and graphene

Mark scheme: 07.1 = “fullerenes and graphene”.

💡 Key knowledge

• Graphene is a single layer of carbon atoms in a hexagonal lattice.
• Fullerenes are carbon structures made from rings (often hexagons plus some pentagons to make a closed shape).
• Diamond is a giant covalent structure but not hexagonal rings (each carbon bonds to 4 others in a tetrahedral arrangement).
• Silica (SiO₂) is not a carbon allotrope and does not have the graphene-style hexagonal rings.

❌ Common errors

• Ticking diamond and graphite: graphite does have hexagonal layers, but diamond does not — the question says both.
• Choosing an option because it “sounds nano”: nanotubes are related to graphene/graphite, but the pair includes silica which breaks the “both” condition.

🧠 Exam technique

• Underline both in the question.
• Quick check: graphene = hexagons; graphite = hexagons; fullerenes = rings including hexagons; diamond = no rings.

✅ Full-mark answer (3/3)

Copper has delocalised electrons. These electrons can move through the structure and transfer energy, so thermal energy is conducted through the metal.

💡 Key knowledge

• Metals are a lattice of positive ions surrounded by delocalised electrons.
• When one part is heated, electrons gain kinetic energy and carry it through the metal by moving and colliding.

🧠 Exam technique (how to hit all 3 marks)

• Write the chain: delocalised electrons → move → transfer energy .
• Use the word structure (or lattice) to show you’re linking property to arrangement.
• Keep it about thermal conduction (energy transfer), not just “conducts electricity”.

❌ Common errors (where marks are lost)

• Saying “copper conducts because it has free electrons” but not stating they move through the structure and transfer energy (often only 1 mark).
• Talking only about ions “vibrating” without linking to electron movement (won’t match this mark scheme).
• Confusing thermal conduction with melting: mentioning “strong bonds so it conducts heat” is not creditworthy here.

✅ Full-mark answer (3/3)

Copper oxide is an ionic compound made of oppositely charged ions (Cu²⁺ and O²⁻) in a giant ionic lattice. There are strong electrostatic forces of attraction between the ions, so a large amount of energy is needed to overcome/break these forces, giving a high melting point.

💡 Key knowledge

• Ionic lattice = repeating 3D arrangement of ions.
• Melting an ionic compound means overcoming the attractions between ions, not breaking molecules apart.
• High melting point happens because there are many strong attractions throughout the structure.

🧠 Exam technique

• Use this sentence frame to secure marks:
  giant ionic lattice → oppositely charged ions → strong electrostatic attraction → lots of energy
• Add “in the lattice / in all directions” to show it’s a giant structure, not just one pair of ions.

❌ Common errors

• Writing “strong covalent bonds” (CuO is ionic at GCSE level for this question).
• Saying only “strong forces” without stating between oppositely charged ions (usually loses a mark).
• Forgetting the energy link: you must say lots of energy is needed to overcome/break the forces.

✅ Full-mark answer (3/3)

Water is made of small (simple) molecules. There are weak forces between the molecules (weak intermolecular forces), so only a small amount of energy is needed to overcome these forces and separate the molecules, giving a low melting point.

💡 Key knowledge

• In water, the covalent O–H bonds are strong, but melting does not break these.
• Melting water mainly involves overcoming forces between molecules (intermolecular forces), which are weak compared with ionic/covalent bonds.

Examiner insight: many students lose marks by mentioning covalent bonds being weak. The exam is testing intermolecular forces.

🧠 Exam technique

• Always start with the structure type: simple molecular.
• Then state the correct forces: weak intermolecular forces (between molecules).
• Finish with the consequence: little energy needed → low melting point.

❌ Common errors (very common on this question)

• “Water has a low melting point because it has weak covalent bonds.” (This is specifically not accepted.)
• Describing “molecules far apart” without linking to weak forces and little energy.
• Confusing melting with boiling and writing about “evaporating” instead of separating molecules in a solid.

🧠 For 3-mark “explain” questions

• Name the structure (metal / ionic lattice / simple molecular).
• Name the particles/forces (delocalised electrons / oppositely charged ions / weak intermolecular forces).
• Link to energy (transfer energy / lots of energy needed / little energy needed).

💡 Keywords the mark scheme rewards

• delocalised electrons
• move through the structure
• transfer energy
• strong electrostatic attraction
• oppositely charged ions
• weak intermolecular forces
• little / large amount of energy required

❌ Top traps

• For water: mentioning covalent bonds instead of forces between molecules.
• For CuO: forgetting it’s a lattice with many attractions, not just one bond.
• For copper: writing about electricity only; you must say thermal energy transfer.