Impure Substance - GCSE Chemistry Definition

An impure substance in chemistry is a material that contains more than one type of particle. Unlike a pure substance, which has only one kind of atom or molecule, an impure substance is a mixture of different substances. These can be elements or compounds, and they are not chemically bonded together. Impure substances can have varying properties, for example the boiling and melting points, unlike pure substances which have constant boiling or melting points. Examples of impure substances include seawater, which contains water and various salts, and polluted air, which is a mixture of different gases and particles. Understanding impurities is important because they can affect how a substance behaves in chemical reactions and in everyday uses.