Solids, liquids and gases Cambridge IGCSE Chemistry (9–1) revision
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In plain words
Everything is made of tiny particles. Whether something is a solid, a liquid or a gas comes down to two things: how close together the particles are, and how freely they can move. Think of a packed lift (solid), a busy corridor (liquid) and a playground (gas).
Three things to know
- Solid: particles packed close together in a regular pattern, vibrating on the spot. Liquid: close together but jumbled, sliding past each other. Gas: far apart, moving fast in all directions.
- Heating gives particles more energy. While a pure substance melts or boils its temperature stays the same: the energy is used to separate the particles.
- Gas pressure is caused by particles hitting the walls of the container. Heat a gas or squash it into a smaller space and the pressure rises.
Tips and tricks
- Describe a state with two things every time: how the particles are arranged, and how they move.
- On a heating curve, the flat parts are where the state is changing. The temperature only rises again once it has all melted or boiled.
It lands in your notebook with its questions as flashcards.
Solids, liquids and gases: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
In which state are the particles close together but able to move past each other?
In a liquid the particles touch but are not fixed in place.
What is the change from gas to liquid called?
Condensation is a gas turning into a liquid as it cools.
What happens to the temperature of a pure solid while it is melting?
The energy goes into separating the particles, not into raising the temperature.
What is sublimation?
The substance misses out the liquid state.
Why does a gas spread out to fill its container?
Gas particles are far apart and move freely and randomly.
A gas is squashed into half the volume at the same temperature. What happens to its pressure?
The particles hit the walls more often in the smaller space.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 9 marks. Write your answers on paper, then check them.
Solids, liquids and gases
Cambridge IGCSE Chemistry (9–1) 0971 · 9 marks · papermunch.org
Name ______________________________ Date ______________
Describe the arrangement and movement of the particles in a liquid.[2]
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Close together (touching) and randomly arranged; they move around and slide past each other.
Explain why a gas is easy to compress but a solid is not.[2]
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The particles of a gas are far apart, so they can be pushed closer together. In a solid they are already touching.
A solid is heated steadily until it has all boiled. Describe the shape of the graph of temperature against time.[3]
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It rises, stays level while the solid melts, rises again while it is a liquid, then stays level again while it boils.
A gas in a sealed container is heated. Explain why its pressure rises.[2]
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The particles gain energy and move faster, so they hit the walls more often and harder.
Answers: Solids, liquids and gases
- 1. Close together (touching) and randomly arranged; they move around and slide past each other.
- 2. The particles of a gas are far apart, so they can be pushed closer together. In a solid they are already touching.
- 3. It rises, stays level while the solid melts, rises again while it is a liquid, then stays level again while it boils.
- 4. The particles gain energy and move faster, so they hit the walls more often and harder.