Describe two limitations of the particle model when used to represent the three states of matter.

WJEC GCSE Chemistry (Wales) — 2.1 Bonding, structure and properties · Describe · 4 marks · View as Markdown

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

The particle model represents particles as small solid spheres to explain changes of state such as melting and boiling.

Model answer (4 marks)

1. The model shows no forces between the particles.
2. All particles are represented as spheres, whereas real particles are not all spherical.
3. The spheres in the model are shown as solid, but real particles are not solid spheres.
4. The model does not explain why atoms of some elements react with one another.

Examiner tips

  • Use the exact wording from the mark scheme; each point counts as one mark.
  • Keep each limitation brief and separate with a number or bullet for clarity.

Common mistakes

  • Writing the limitations in a single long sentence instead of separate points.
  • Using vague terms like "not accurate" instead of the specific issues listed in the mark scheme.

Mark scheme (4 marks)

  1. The model shows no forces between the particles
  2. All particles are represented as spheres (but real particles are not all spherical)
  3. The spheres in the model are shown as solid, but real particles are not solid spheres
  4. The model does not explain why atoms of some elements react with one another

Key terms in this question

particle model · states of matter

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