Chapter 2 · Chemistry
Exploring Mixtures and their Separation: Chapter Introduction
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Muddy water settles but milk never does: particle size decides how a mixture behaves. Solutions, colloids and suspensions, and the ways to separate them.
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Key points
- Most materials around us are mixtures: air, sea water, milk, soil.
- Solution: particles < 1 nm, invisible, never settle (salt water).
- Suspension: particles > 1000 nm, visible, settle under gravity (muddy water).
- Colloid: 1-1000 nm, do not settle but scatter light, the Tyndall effect (milk). Separation methods match the mixture: filtration, evaporation, chromatography, distillation, magnetic separation.
Particle size decides
| Type | Particle size | Settles? | Light beam | Example |
|---|---|---|---|---|
| Solution | < 1 nm | No | Not visible | Salt water |
| Colloid | 1-1000 nm | No | Visible (scattered) | Milk |
| Suspension | > 1000 nm | Yes | Blocked/scattered | Muddy water |
Separating mixtures
| Method | Separates | Example |
|---|---|---|
| Filtration | insoluble solid from liquid | sand from water |
| Evaporation | dissolved solid from solvent | salt from sea water |
| Chromatography | colours in a mixture | inks, dyes |
| Distillation | liquids with different boiling points | water from salt water |
| Magnet | magnetic from non-magnetic | iron filings from sand |
Quick quiz
4 questions. Choose an answer for each, then submit to see your score and the explanations.