GCSE Physics · AQA 8463 · Topic 4.3
Particle model of matter
Key points
- Density is mass per unit volume: . Solids are usually densest because their particles are packed closest together.
- Changes of state are physical changes that conserve mass and can be reversed.
- Internal energy is the total kinetic and potential energy of all the particles in a system.
- Heating raises the temperature () or changes the state (), not both at once.
- Specific latent heat is the energy needed to change the state of 1 kg without changing temperature (fusion: solid/liquid; vaporisation: liquid/gas).
- Gas particles move randomly and their collisions with walls cause pressure. Higher temperature means faster particles and higher pressure (at constant volume).
- For a fixed mass of gas at constant temperature, = constant.
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The particle model treats every material as a huge number of tiny particles in constant motion. With this one simple picture you can explain density, changes of state, heating and why a gas pushes on the walls of its container.
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