Try Chemical Decomposition

Third step in classification [1flowch4.gif] As mentioned previously, materials which are not broken up into components or separated into components by going through phase change operations are considered to be pure substances. It turns out that pure substances can be of two types. The two types of pure substances are called compounds and elements. Both compounds and elements are pure substances.

The test for whether a pure substance is a compound or an element is to find out whether it can be decomposed. If a pure substance can be chemically decomposed it is classified as a compound. If a pure substance cannot be chemically decomposed it is classified as an element.

Water is an example of a compound. It is an example of a compound because it is a pure substance that can be decomposed into components. In the electrolysis exercise in this lesson water is separated into its components. When an electric current is passed through water, it is able to separate the hydrogen from the oxygen. Because water is a pure substance that can be decomposed, we classify it as a compound.

Elements, on the other hand, are pure substances which cannot be decomposed by electrolysis or any other kind of chemical reaction.

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E-mail instructor: Sue Eggling