Describe the arrangement and movement of particles in a solid and explain how these change when the solid melts to form a liquid.

Edexcel GCSE Chemistry (1CH0) — 1.1 States of matter · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

In a solid the particles are arranged in a regular, fixed lattice.
They vibrate about their fixed positions but do not move from place to place.
When the solid melts the regular arrangement is broken down.
The particles are no longer in fixed positions and can move past and around each other.
The particles gain energy, move more quickly and the forces of attraction between them are partially overcome.

Examiner tips

  • Use the word "lattice" for the arrangement; mention vibration but no flow; state that melting breaks the lattice and allows particle movement; note energy gain and overcoming of forces.
  • Keep the answer concise – 4 points can be covered in 4 short sentences.

Common mistakes

  • Saying particles "flow" in a solid; describing the solid as a liquid before melting; omitting the energy gain or the overcoming of forces.

Mark scheme (4 marks)

  1. In a solid, particles are arranged in a regular (fixed/ordered) pattern/lattice
  2. In a solid, particles vibrate (but do not move from place to place / do not flow)
  3. On melting, the regular arrangement is broken down / particles are no longer in fixed positions and can move past / around each other
  4. On melting, the particles gain energy / move more quickly / forces of attraction between particles are (partially) overcome

Key terms in this question

arrangement · particles

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