Substances and Mixtures. Matter can be classified into two broad categories: pure substances and mixtures. A pure substance is a form of matter that has an uniform composition and properties that are constant throughout the sample. Elements and compounds are both example of pure substances.ecall that a solution is a mixture of substances in such a way that the final product has the same composition throughout. Remember the example of vinegar that is 5%, by mass, acetic acid in water. This clear liquid is a solution since light easily passes through it and it never separates.