Compare the arrangement and movement of particles in a solid with those in a gas, and use these differences to explain why solids have a much higher density than gases.

Cambridge International IGCSE Chemistry (0620) — 1.1 Solids, liquids and gases · Compare · 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 closely and regularly packed, forming a fixed lattice. They can only vibrate about their fixed positions. In a gas the particles are widely spaced, moving rapidly and randomly in all directions. Because the particles in a solid are so tightly packed, a given volume contains many more particles than the same volume of gas, giving solids a much higher mass and therefore a higher density.

Examiner tips

  • Use the word ‘compare’ to list contrasting features; include packing, motion and density explanation.
  • Show the link between packing density and mass per unit volume to justify higher density.

Common mistakes

  • Confusing the arrangement of particles in a liquid with that in a solid; describing liquid particles as fixed.
  • Failing to mention that gas particles move freely in all directions; or not linking packing to density.

Mark scheme (4 marks)

  1. Particles in a solid are closely/tightly packed together (regular arrangement)
  2. Particles in a gas are far apart / widely spaced / have large distances between them (random arrangement)
  3. Particles in a solid only vibrate about fixed positions; particles in a gas move rapidly/freely in all directions
  4. Because solid particles are closely packed, a given volume contains many more particles than the same volume of gas, so the mass (and therefore density) is much greater

Key terms in this question

density · arrangement · particles · solid · gas

Related

More Solids, liquids and gases questions

▶ Try answering this question with AI marking (free) →