What is a mixture?
A mixture is made of two or more substances that are physically combined but not chemically joined. Each substance in a mixture keeps its own properties. Because they are not chemically bonded, the parts of a mixture can be separated again by simple physical methods. The substances can be mixed in any proportion.
Key idea
In a mixture, substances are mixed but not chemically combined, so each keeps its own properties and can be separated by physical means.
Everyday mixtures
- Air – a mixture of gases such as nitrogen, oxygen and carbon dioxide.
- Sea water – water with dissolved salt and other substances.
- Sand and salt – two solids simply mixed together.
- A rojak – many foods tossed together, each still tasting like itself.
Separating mixtures
Because the substances are not chemically bonded, we can separate them using their different physical properties:
| Method | Used for |
|---|---|
| Filtration | Separating an insoluble solid from a liquid (e.g. sand from water) |
| Evaporation | Getting a dissolved solid from a solution (e.g. salt from salt water) |
| Using a magnet | Separating a magnetic material (e.g. iron filings from sand) |
Example
To get clean water from muddy water, we filter out the mud. To get salt from salt water, we evaporate the water and the salt is left behind.
Remember
- A mixture is not chemically joined.
- Each substance keeps its own properties.
- Mixtures can be made in any proportion.
- Physical methods like filtration and evaporation can separate mixtures.