In everyday life the word pure is used loosely. A label that says pure orange juice or pure spring water usually means that nothing has been added, or that the product is natural. A scientist uses the word in a much stricter way.
In chemistry a pure substance is made of only one element or only one compound, with nothing else mixed in. Elements and compounds are pure substances. A mixture contains two or more different substances that are not chemically joined, so a mixture is an impure substance.
This means that pure orange juice is not pure to a chemist, because it contains water, sugar, acids and many other substances. The same is true of mineral water, which has dissolved salts in it. A clear solution such as salt dissolved in water is also a mixture, because it contains two different substances: salt and water. Dissolving a substance does not make it pure.
