Types of substances

'Pure' has a specific meaning in chemistry.

A substance is a single element or compound not mixed with any other substance.

A contains two or more different substances mixed together, usually easy to separate.

Pure substances	Mixtures
Diamond only contains the element carbon.	Air is a mixture of oxygen, carbon dioxide, nitrogen and other trace gases.
Water only contains the compound water.	Mineral water is a mixture of water and dissolved salts.
Table salt only contains the compound sodium chloride.	Milk is a mixture of water, lactose, fat and minerals such as salt.

Pure substances	Diamond only contains the element carbon.
Mixtures	Air is a mixture of oxygen, carbon dioxide, nitrogen and other trace gases.

Pure substances	Water only contains the compound water.
Mixtures	Mineral water is a mixture of water and dissolved salts.

Pure substances	Table salt only contains the compound sodium chloride.
Mixtures	Milk is a mixture of water, lactose, fat and minerals such as salt.

Here are some examples of pure substances and mixtures.

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