Fullerenes are a form of carbon. Buckminsterfullerene (C₆₀) is a well-known fullerene. Explain why buckminsterfullerene has a low melting point compared to diamond.

AQA GCSE Chemistry (8462) — 4.2.3 Structure and bonding of carbon · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Both buckminsterfullerene and diamond are made entirely of carbon atoms held together by covalent bonds.

Model answer (4 marks)

Buckminsterfullerene is made of discrete C₆₀ molecules, not a continuous network. The molecules are held together only by weak van der Waals forces. Consequently, only a small amount of energy is required to overcome these intermolecular forces and melt the solid. In contrast, diamond is a giant covalent network; every carbon atom is bonded to four others by strong covalent bonds. Breaking this extensive network requires a large amount of energy, giving diamond a very high melting point.

Examiner tips

  • Use the word ‘discrete’ or ‘separate’ to show the molecular nature of C₆₀. Mention ‘van der Waals forces’ as the weak intermolecular attraction. Explain that little energy is needed to break these forces. Contrast with the ‘giant covalent network’ of diamond and the high energy required to break it.

Common mistakes

  • Confusing the type of bonding (covalent vs. van der Waals) within the material. Forgetting to mention that C₆₀ consists of separate molecules. Overstating the strength of the forces in buckminsterfullerene or underestimating the covalent bonds in diamond.

Mark scheme (4 marks)

  1. Buckminsterfullerene consists of individual / separate molecules (whereas diamond is a giant covalent structure)
  2. There are (weak) intermolecular forces between the C₆₀ molecules
  3. Little energy is needed to overcome these intermolecular forces
  4. Diamond has many strong covalent bonds in a giant structure which require a lot of energy to break, so has a high melting point (by contrast)

Key terms in this question

fullerenes

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