AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
The three states of matter can be represented by a simple model. In this…
Full specification wording
The three states of matter: The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres.
The simple particle model pictures matter as tiny solid spheres.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 9
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The simple particle model pictures matter as tiny solid spheres. In a solid, the spheres are packed closely in a regular arrangement and only vibrate about fixed positions, so the shape and volume stay fixed. In a liquid, the spheres are still close but randomly arranged and can slide past one another, so the volume is fixed but the shape flows to fit the container. In a gas, the spheres are far apart, randomly arranged and move quickly in all directions, so both shape and volume change to fill the container. For example, ice, water and steam all contain H₂O particles, but the spacing and motion of the spheres differ. The model is useful but limited: it ignores forces, particle size and the internal structure of atoms.
What earns the marks
- States the arrangement of particles in a solid as close together in a regular pattern, with particles vibrating about fixed positions.
- Describes the arrangement in a liquid as close together but random, with particles able to move and slide past one another.
- Describes the arrangement in a gas as far apart, random and moving quickly in all directions.
- Links each arrangement to the observable properties of shape and volume: fixed shape and volume for a solid, fixed volume but flowing shape for a liquid, and filling the container for a gas.
- Recognises that the same substance in different states contains the same particles, for example H₂O in ice, water and steam.
- Explains that the simple model represents particles as small solid spheres and does not show forces, particle size or internal structure.
Common mistakes and how to put them right
Saying that particles in a liquid are far apart.
Put it right by stating that liquid particles remain close together but are randomly arranged and can move past one another.
Saying that particles melt or freeze.
Put it right by stating that the particles themselves do not change; the arrangement, spacing and motion of the particles change.
Drawing gas particles evenly spaced in a regular grid.
Put it right by showing gas particles far apart and randomly arranged.
Exam tips
- When asked to describe a state, name both the arrangement and the motion of the particles, then link these to shape and volume.
- Use comparative language such as close together, far apart, regular, random, vibrate and move quickly to make the description precise.
- If a question asks about the model's limitations, mention that it does not show forces between particles or the internal structure of atoms.
Try the lesson
The start of the The three states of matter: The three states of matter can be represented by a simple model. In this model, particles are represented by small solid spheres. lesson, made from checked teaching notes for this specification point.
Have a go first
In the simple model of the three states of matter, what do the small solid spheres represent?
Listen
The simple particle model pictures matter as tiny solid spheres. In a solid, the spheres are packed closely in a regular arrangement and only vibrate about fixed positions, so the shape and volume stay fixed. In a liquid, the spheres are still close but randomly arranged and can slide past one another, so the volume is fixed but the shape flows to fit the container. In a gas, the spheres are far apart, randomly arranged and move quickly in all directions, so both shape and volume change to fill the container. For example, ice, water and steam all contain H₂O particles, but the spacing and motion of the spheres differ. The model is useful but limited: it ignores forces, particle size and the internal structure of atoms. A strong answer earns marks for these points. States the arrangement of particles in a solid as close together in a regular pattern, with particles vibrating about fixed positions. Describes the arrangement in a liquid as close together but random, with particles able to move and slide past one another. Describes the arrangement in a gas as far apart, random and moving quickly in all directions. Links each arrangement to the observable properties of shape and volume: fixed shape and volume for a solid, fixed volume but flowing shape for a liquid, and filling the container for a gas. A common slip: Saying that particles in a liquid are far apart. Instead, stating that liquid particles remain close together but are randomly arranged and can move past one another. Exam tip: When asked to describe a state, name both the arrangement and the motion of the particles, then link these to shape and volume.
See it
Key words
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Properties of solids, liquids and gases
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Use and limitations of scientific models
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Conservation of particles during changes of state
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See every definition
- Properties of solids, liquids and gases
- A solid has a fixed shape and volume, a liquid has a fixed volume but a shape that flows to fit the container, and a gas changes both shape and volume to fill the container.
- Use and limitations of scientific models
- The simple model represents particles as small solid spheres, but it ignores forces, particle size and the internal structure of atoms.
- Conservation of particles during changes of state
- Ice, water and steam all contain H₂O particles, but the spacing and motion of the spheres differ.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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