Who this is for: Cambridge IGCSE Chemistry (0620) students who mix up particle arrangement in solids, liquids and gases — or lose marks describing changes of state without linking energy and bonding.
What query it owns: how to understand and revise solids, liquids and gases in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the particle-model revision-guide angle, while Tutopiya’s Solids, Liquids and Gases subtopic page owns the learning resource and the free Solids, Liquids and Gases quiz owns the practice.

Solids, liquids and gases are the foundation of the States of Matter unit in Cambridge IGCSE Chemistry (0620). Examiners expect you to describe particle arrangement, movement and energy for each state, and to explain melting, boiling and condensation using the particle model — not vague “particles move faster” answers. This guide covers the core ideas, exam command words, and where to practise each skill.

Key takeaways

• Solids — particles close together, fixed positions, vibrate; liquids — close together, slide past each other; gases — far apart, random rapid movement.
• Changes of state are physical — no new substance forms; energy changes break or allow intermolecular forces, not covalent bonds (in simple cases).
• Heating curves link temperature plateaus to latent heat at melting/boiling points.
• Always pair particle descriptions with arrangement + movement + energy in describe answers.
• Confirm with the Solids, Liquids and Gases quiz after reading the subtopic notes.

What are solids, liquids and gases in Cambridge IGCSE Chemistry?

Solids, liquids and gases are the three common states of matter described by the particle model: substances consist of tiny particles whose arrangement and movement depend on temperature and pressure. In Cambridge IGCSE Chemistry (0620) you must compare all three states and explain changes between them using kinetic theory.

Read the full explanation on Tutopiya’s Solids, Liquids and Gases subtopic page before attempting questions.

The core ideas you must master

State	Arrangement	Movement	Energy (relative)
Solid	Close, regular lattice	Vibrate about fixed positions	Lowest
Liquid	Close, irregular	Slide over each other	Intermediate
Gas	Far apart	Random, rapid	Highest

How to answer particle-model questions — step by step

1. Name the state or change of state the question targets.
2. Describe arrangement — close/far apart, ordered/random.
3. Describe movement — vibrate, slide, or move freely.
4. Link energy — heating supplies energy so particles move more; cooling removes energy.
5. For changes of state, state that temperature stays constant at melting/boiling while energy breaks intermolecular forces.
6. Check yourself with the free Solids, Liquids and Gases quiz.

Changes of state — summary table

Change	From → To	Energy supplied or removed?	Temperature at change
Melting	Solid → Liquid	Supplied	Constant (melting point)
Boiling	Liquid → Gas	Supplied	Constant (boiling point)
Condensation	Gas → Liquid	Removed	Constant
Freezing	Liquid → Solid	Removed	Constant

Solids, liquids and gases in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical stem
Describe	Particle arrangement and movement	”Describe the arrangement and movement of particles in a gas.”
Explain	Cause and effect with energy	”Explain why the temperature stays constant during boiling.”
State	Short factual answer	”State the process when a liquid becomes a gas.”
Complete the heating curve	Label changes of state	”Label X on the heating curve.”

Worked exam-style stems (how to answer the wording)

1. “Describe the arrangement and movement of particles in a solid.” Target: particles close together in a regular pattern; vibrate about fixed positions. Mark-scheme reward: both arrangement and movement — “particles are still” alone loses marks.
2. “Explain why the temperature of water stays at 100 °C while it boils.” Target: energy supplied breaks intermolecular forces (overcoming attraction) rather than increasing kinetic energy; temperature measures average kinetic energy, which stays constant during the change of state.
3. “A substance is cooled from 80 °C to −10 °C. State what happens to particle movement.” Target: particles move more slowly / have less kinetic energy. State = concise — no long explain chain needed.

Practise authentic stems on the States of Matter topical past paper questions and the Solids, Liquids and Gases quiz.

How this subtopic connects to Diffusion

Particle movement in gases and liquids underpins Diffusion — the spreading of particles from high to low concentration. Master solids, liquids and gases first; then move to diffusion and the Diffusion quiz. The Cambridge IGCSE Chemistry resource hub links both subtopics.

Common mistakes students make

• Describing only movement without arrangement in describe answers.
• Saying particles expand when heated — the substance expands; particles move further apart in gases, not in fixed lattices.
• Confusing boiling (throughout liquid) with evaporation (surface only).
• Claiming covalent bonds break during melting of simple molecular substances when intermolecular forces break (context-dependent — know your substance type).
• Skipping the Solids, Liquids and Gases quiz after note-reading.

When you need more support

If particle-model describe questions keep scoring partial marks after two practice cycles, work through the States of Matter topical past paper questions and book a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

Is the particle model hard in Cambridge IGCSE Chemistry? No — the ideas are straightforward. Marks are lost when students omit arrangement or fail to link energy to changes of state.

What is the difference between evaporation and boiling? Evaporation occurs at the surface below boiling point; boiling occurs throughout the liquid at the boiling point.

Do particles stop moving in a solid? No — they vibrate about fixed positions; they do not have zero energy except at absolute zero (not examined at IGCSE).

How do I revise solids, liquids and gases effectively? Read the subtopic notes, practise describe/explain stems from the topical bank, then take the Solids, Liquids and Gases quiz.

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