AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 8

✅ Correct Answer

Spherical

Also allowed: ball-shaped

❌ Common Errors & Examiner Notes

• Writing "round" or "circular" — these describe 2D shapes and receive zero marks.
• Writing "hexagonal" — rings inside the fullerene are hexagonal and pentagonal, but the overall molecule shape is spherical.

✅ Any ONE of the following accepted answers:

• Drug delivery (into/round the body)
• Lubricants
• Catalysts (due to high surface-area-to-volume ratio)
• Hydrogen storage
• Anti-oxidants
• Reduction of bacterial growth
• Strengthening materials (cylindrical fullerenes / nanotubes)

🧠 Exam Technique

The question says "Give one use". Never write multiple guesses; if one is incorrect, you risk cancelling out your correct answer. "Drug delivery" or "lubricants" are the most reliable, standard recall points.

✅ Completed Structural Formula

Each single shared pair of electrons in Figure 13 becomes a single line ( — ). The central carbon is already double-bonded to oxygen ( C=O ).

🧠 Exam Technique: Reading Dot-and-Cross

• 1 pair of shared electrons (ו) = 1 single covalent bond ( — ).
• Figure 13 shows 3 C–H bonds on the left carbon and 3 C–H bonds on the right carbon.
• Ensure every hydrogen has one bond and all three carbons have four bonds total.

✅ Correct Answer

C₃H₆O

Also allowed: CH₃COCH₃ or elements in any order (e.g. H₆C₃O ).

📐 Step-by-Step Counting

1. Count carbon atoms: 3 black central circles = C₃
2. Count hydrogen atoms: 3 on left + 3 on right = H₆
3. Count oxygen atoms: 1 at the bottom = O
4. Combine using subscript numerals: C₃H₆O

❌ Common Errors

• Writing numbers on the baseline or as superscripts instead of subscripts (e.g. C3H6O or C³H⁶O).
• Miscounting hydrogen atoms (often writing 5 or 8).

✅ Correct Checkbox Choice

☑ The intermolecular forces are weak.

💡 Key Knowledge

Propanone is a small covalent molecule. When it boils, the strong covalent bonds within the molecules do NOT break. Only the weak intermolecular forces between separate molecules are overcome.

❌ Common Misconception

Students regularly tick "The covalent bonds are weak". Covalent bonds are extremely strong! Boiling simple molecules never breaks covalent bonds.

💡 Part 1: Why Graphite Conducts Electricity

1. Graphite has a giant covalent / macromolecular structure.
2. Each carbon atom forms only three covalent bonds to other carbon atoms (hexagonal rings).
3. This leaves one electron per carbon atom delocalised (free).
4. These delocalised electrons can move throughout the structure.
5. They carry electrical charge through the material.

💡 Part 2: Why Graphite is Soft and Slippery

1. Graphite is arranged in layers of hexagonal rings.
2. There are no covalent bonds between the layers (only weak intermolecular forces).
3. Because these forces are weak, the layers can easily slide over each other.
4. This makes graphite feel soft, slippery, and suitable as a solid lubricant or in pencil lead.

✅ Model 6/6 Answer Template

"Graphite is a giant covalent structure made of carbon atoms arranged in hexagonal layers. Each carbon atom forms three covalent bonds, leaving one delocalised electron per atom. Because these delocalised electrons are free to move throughout the structure, they carry electrical charge, making graphite a good electrical conductor."

"Furthermore, between the layers there are only weak intermolecular forces and no covalent bonds. Therefore, the layers can easily slide over one another, which makes graphite soft and slippery."

❌ Costly Mistakes to Avoid

• Saying "ions move": Graphite is made purely of neutral carbon atoms; electrical current is carried by delocalised electrons, never ions.
• Saying "covalent bonds break when layers slide": Only the weak forces between layers are overcome; the covalent bonds inside each sheet remain intact.
• Missing the cause: Stating "it has delocalised electrons" without stating "because each carbon only forms 3 bonds" misses key AO1 marking points.