GCSE Physics · AQA 8463 · Topic 4.3.1
Changes of state and the particle model
Key points
- Density: , in kg/m³ (or g/cm³). For an irregular object, find the volume by displacement of water in a measuring cylinder or eureka can.
- In a solid, particles are close and vibrate about fixed positions; in a liquid they are close but move past each other; in a gas they are far apart and move fast and randomly.
- Changes of state: melting, freezing, boiling/evaporating, condensing and sublimating.
- These are physical changes: the material keeps its original properties if the change is reversed, and mass is conserved.
- Required practical: measure the density of regular and irregular solids and of liquids.
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Why does a block of iron sink while a log floats, and why is steam so much less dense than water? The answer lies in how closely the particles are packed. This sub-topic links density to the particle model and to the changes of state…
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