purity

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In chemistry, a substance that contains only one type of material. Pure substances may be simple elements made up of atoms such as carbon or silver. They may be molecules, like oxygen or hydrogen, or they may be compounds like water. Compounds are pure substances because each particle is the same type.

Pure substances have individual properties and characteristics. These properties can be both physical, such as boiling point and melting point, or chemical such as the way they react with other substances. Mixtures contain more than one type of substance and so have the properties of each component. An example would be the air in the atmosphere, which is a mixture of many gases including nitrogen, oxygen, carbon dioxide, and the noble gases (rare gases). The process of purification separates the components of a mixture, and removes impurities from a substance.

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