Chemistry
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Atoms and molecules
Molecules in mixtures and pure substances
The concept of molecule allows to give a more precise definition of mixtures and pure substances.
1) Pure substances
A pure substance is a substance (solid, liquid or gas) that consists only of one kind of molecule.
examples:
- Distilled water is a pure substance because it consists only of water molecules.
- Dioxygen is a pure substance because it consists only of dioxygen molecules
2) Mixtures
A mixture is a substance (solid, liquid or gas) which consists of several kinds of molecules.
examples:
- Air is a mixture because it consists of several kinds of molecules: dioxygen, dinitrogen, carbon dioxide etc..
- The sugar water is a mixture because it consists of two kinds of molecules: water and sugar (saccharose).
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