Tiny smoke particles suspended in air inside a sealed glass chamber are illuminated by a bright lateral light source and viewed under a microscope. The smoke particles are observed to move in a continuous, erratic, and zig-zag fashion.
State the name given to this erratic motion of suspended particles.
Explain how the observation of this motion provides direct evidence that air is made of tiny, rapidly moving molecules.
The table below shows physical observations of the three common states of matter:
| State of Matter | Shape | Density |
|---|---|---|
| Solid | Retains a fixed, definite shape | High density |
| Liquid | Flows to take the shape of the container's base | High density |
| Gas | Expands to completely fill any container | Very low density |
Explain these observations by describing the spacing, arrangement, and motion of the particles in a solid, a liquid, and a gas.
51 exam-style questions on Edexcel IGCSE Physics Ideal gas molecules. Each one has a worked solution and a mark scheme showing where the marks go.