Explain why a substance in the liquid state can flow and take the shape of its container, but a substance in the solid state cannot.

Edexcel GCSE Chemistry (1CH0) — 1.1 States of matter · Explain · 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 liquid the particles are close together but can move or slide past each other. This mobility allows the liquid to flow and to adopt the shape of its container.
In a solid the particles are held in fixed positions in a regular lattice by strong forces. They can only vibrate about their fixed positions, so they cannot flow or change shape.

Examiner tips

Use the key terms ‘move/slide past each other’ for liquids and ‘fixed positions/regular lattice’ for solids.
Show the causal link: mobility → flow → shape of container.
Keep the answer concise – 4 marks only.
Use UK spelling (e.g. ‘vibrations’).

Common mistakes

Confusing the behaviour of gases with liquids; forgetting to mention the fixed lattice in solids.
Using vague phrases like ‘particles are close together’ without explaining the difference in motion.
Writing a long paragraph instead of clear, separate points.

Mark scheme (4 marks)

In a liquid, particles are close together but able to move/slide past each other
This allows a liquid to flow and adopt the shape of its container
In a solid, particles are held in fixed positions / a regular lattice by strong forces between them
Because solid particles can only vibrate about their fixed positions, they cannot flow or change shape

Key terms in this question

liquid · solid · flow