Mixtures all around
Think about what air is made of. Nitrogen, oxygen, argon and carbon dioxide are all in it; so is water vapour, and so is dust. Air is not one substance — it is several substances mixed together.
A mixture
When two or more substances are present together in some material, that material is called a mixture.
Where this sits against grade 10
Grade 10 sorted matter into pure substances and mixtures, and you already know elements and compounds are pure. The line between the two halves is worth restating before this chapter builds on it.
A pure substance
One kind of matter throughout. Its parts are chemically joined in a fixed proportion, and it cannot be split by physical means.
Examples: copper, oxygen, water, sodium chloride
A mixture
Two or more substances merely mingled. There is no fixed proportion, and each substance keeps its own properties.
Examples: air, soil, sea water, tea
Pure substances are the rare ones
It is easy to get the impression from a laboratory that pure substances are normal and mixtures are unusual. Outside, it is the other way round. What is actually around you is almost all mixture:
- In the environment — the air, the soil, sea water, river water, rock
- In what you drink — soft drinks, fruit juice, tea, coffee
- In what you eat — ice cream, yoghurt, fruit salad
Pure substances are scarce in the natural world. Mixtures are what there is.