AQA GCSE Chemistry Chemistry Paper 1 (Higher), 2022: Question 3

✅ Correct Answers

• It is a giant structure (or macromolecular / giant lattice) [1 mark]
• It contains covalent bonds [1 mark]
• Each carbon atom forms four bonds [1 mark]

💡 Key Knowledge

Carbon is in Group 4 of the periodic table, meaning it has 4 electrons in its outer shell. In diamond, every single carbon atom shares all 4 of its outer electrons to form strong covalent bonds with 4 other carbon atoms in a rigid, 3D tetrahedral giant covalent network.

🧠 Exam Technique

To get all 3 marks, you must mention three distinct features: the scale of the structure (giant), the type of bond (covalent), and the specific number of bonds per atom (four).

❌ Common Errors

Do not confuse diamond with graphite! Students often lose marks by mentioning "layers", "weak intermolecular forces", or "delocalised electrons". None of these exist in diamond.

✅ Correct Answers

• The covalent bonds are strong [1 mark]
• Many covalent bonds must be broken [1 mark]
• Therefore, a lot of energy is required to break them [1 mark]

🧠 The 3-Step Melting Point Template

Whenever GCSE questions ask why a substance has a high melting/boiling point, always structure your answer using this 3-step formula:

1. Identify the type of bond and state that it is strong.
2. State that there are many of these bonds that must be broken.
3. Conclude that a lot of energy is needed.

❌ Common Errors

The "Intermolecular" Trap: Never mention "intermolecular forces" or "weak forces between molecules" when discussing diamond. Diamond is a giant covalent structure, not a simple molecule. Mentioning intermolecular forces here will instantly cost you marks!

✅ 03.3 Correct Answer

☑️ Fullerene [1 mark]

The hollow cage-like structure shown in Figure 6 (C₇₀) is a fullerene. Graphene is a single 2D sheet, nanotubes are cylinders, and polymers are long chains.

✅ 03.4 Correct Answer (Any one of:)

• C₇₀ is hollow (acts as a cage / traps the drug) [1 mark]
• C₇₀ is unreactive [1 mark]
• C₇₀ is not toxic [1 mark]
• C₇₀ has a large surface area to volume ratio [1 mark]

🧠 Exam Technique: Read the "Ignore" Rules

The examiner's mark scheme explicitly states to ignore references to ease of movement around the body. Focus instead on the physical structure (hollow cage to carry the drug safely) or chemical safety (non-toxic, unreactive).

❌ Common Calculation Traps

The Multiplication Error: Many students incorrectly multiply 1 mole of carbon atoms by 70, calculating 1 × 70 × (6.02 × 10²³) = 4.21 × 10²⁵ .

Think logically: It takes 70 individual carbon atoms to build just one C₇₀ molecule. Therefore, the total number of C₇₀ molecules must be much smaller than the starting number of carbon atoms!

🧠 Error Carried Forward (ECF)

If you make a mistake in Step 1 (e.g., you write down an incorrect number of moles), you can still get the remaining 2 marks if you correctly multiply your incorrect mole value by 6.02 × 10²³ . Always show your working clearly so the examiner can award these method marks!