GCSE Chemistry · Edexcel 1CH0 · Topic 2A
States of matter
Key points
- Solids: particles closely packed in a regular pattern, vibrating in fixed positions. Liquids: close together but random and able to move past each other. Gases: far apart, moving quickly in all directions.
- Changes of state: melting, freezing, boiling/evaporating, condensing, and sublimation (solid straight to gas).
- Heating gives particles more energy, so forces between them are overcome. The stronger the forces, the higher the melting and boiling points.
- Use melting and boiling points to predict the state at a given temperature: below the melting point it is solid, between the two it is liquid, above the boiling point it is gas.
- Changes of state are physical changes (reversible, no new substances); chemical changes make new substances.
- The simple particle model treats particles as hard spheres with no forces, which is a limitation.
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The particle model explains why solids, liquids and gases behave so differently and what happens when a substance changes state. These notes cover the arrangement and movement of particles, energy changes during changes of state, and…
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