The word 'pure' is used in chemistry in a different way from its everyday meaning. For example, shops sell cartons labelled as ‘pure' orange juice. The label means that the contents are just orange juice, with no other substances added. However, the juice is not pure in the chemical sense, because it contains different substances mixed together. In chemistry:
The substances in a mixture can be elements, or compounds, or both. Being part of a mixture does not change the chemical properties of the substances that are in it.
Mixtures can be separated by physical processes. These processes do not involve chemical reactions, and no new substances are made.