A mixture contains two or more substances that are not chemically combined.

Did you know?
Fireflies, like the one shown below, glow when a chemical reaction within their bodies releases light.
Firefly glowing
Image by Yikrazuul

Mixtures are unlike chemical compounds, because:

The substances in a mixture can be separated using physical methods such as filtration, freezing, and distillation.
There is little or no energy change when a mixture forms.
Mixtures have variable compositions, while compounds have a fixed, definite formula.
When mixed, individual substances keep their properties in a mixture, while if they form a compound their properties can change.

Examples of Common Mixtures:

Sea water - a mixture of water and various salts.
Crude oil - a mixture of organic compounds - mainly hydrocarbons.
Gunpowder - a mixture of potassium nitrate, sulfur and carbon.
Dry Air - a mixture of nitrogen, oxygen, argon, carbon dioxide, neon and tiny traces of other gases. (Air normally also contains water vapor as part of the mixture.)
Ink - a mixture of colored dyes which can be separated using chromatography.

It's possible to get homogeneous mixtures and heterogeneous mixtures.

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