Describe the arrangement and movement of particles in a liquid, and explain why a liquid can flow but cannot be compressed.

Pearson Edexcel International GCSE Chemistry (4CH1) — 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)

Particles in a liquid are close together and in contact with each other.
Particles move randomly and can slide past one another.
A liquid can flow because the particles are not fixed in position and can move past each other.
A liquid cannot be compressed because the particles are already close together and there is no space between them.

Examiner tips

Use the exact phrases "close together" and "in contact" for the first point. Show that particles can "slide past" each other to justify flow. Explain compression by noting the lack of space between particles.
Include the word "randomly" when describing particle movement to hit the full mark.

Common mistakes

Writing that particles are "far apart" or "not touching". Forgetting to mention that particles can slide past each other. Using vague terms like "move freely" instead of "slide past" or "randomly".

Mark scheme (4 marks)

Particles in a liquid are close together / touching / in contact with each other
Particles in a liquid move randomly / can move past / slide past each other
A liquid can flow because particles are not held in fixed positions (and can move past each other)
A liquid cannot be compressed because the particles are already close together / there is no space between particles

Key terms in this question

liquid · particles · compressed