States of Matter
Year 7 ⚛️ Particles & Structure Describe solids, liquids and gases using the particle model.
🧊 The Three States of Matter
All matter is made of particles. The arrangement and movement of these particles explains the properties of solids, liquids and gases.
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed | Takes container shape | Fills container |
| Volume | Fixed | Fixed | Not fixed |
| Particle spacing | Very close (touching) | Close together | Far apart |
| Particle movement | Vibrate in place | Slide past each other | Move rapidly, randomly |
| Compressibility | Not compressible | Not compressible | Highly compressible |
Memory trick: S-L-G = Solid stays, Liquid slides, Gas goes everywhere!
🌡️ Changes of State
When matter changes state, energy is transferred. Heating provides energy to break forces between particles; cooling removes energy and forces re-form.
Change of State Diagram
$$\text{Solid} \xrightarrow{\text{melting}} \text{Liquid} \xrightarrow{\text{boiling/evaporation}} \text{Gas}$$
$$\text{Gas} \xrightarrow{\text{condensation}} \text{Liquid} \xrightarrow{\text{freezing}} \text{Solid}$$
$$\text{Solid} \xrightarrow{\text{sublimation}} \text{Gas} \quad (\text{e.g. dry ice, iodine})$$Key point: Temperature stays constant during a change of state — all energy goes into breaking/forming bonds, not raising temperature.
📊 Heating & Cooling Curves
A heating curve shows how temperature changes as energy is supplied at a constant rate.
Flat regions on a heating curve occur during changes of state — temperature is constant while bonds break.
Sublimation: solid turns directly into gas without passing through liquid. Dry ice (solid CO₂) sublimes at room temperature.
Ready to test yourself? Click the Quiz tab above to practise questions on this topic!
Interactive Demonstration — States of Matter
Select a state to see the particle arrangement.
🧊 States of Matter Particle Simulator
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