All matter can be broadly divided into two major groups “Pure” and “Impure”. The term ‘purity’ has quite a different meaning in chemistry than in our day-to-day life. Normally when we refer to pure water, pure milk, etc., what is implied is that the water, milk etc., are free from harmful substances such as bacteria, fungi, viruses, etc. ‘Purity’ in chemistry is entirely of a different nature. When we say a substance is pure, it means that the substance is made of only one type of constituent particles.

Example: In chemical terms, pure water means that it is made of only one type of molecules i.e., H2O.

As mentioned above matter can be divided into pure and impure substances. The pure substances can be further divided into “Elements” and “Compounds”. The impure substances, commonly called “Mixtures” can also be divided further into ‘Homogeneous’ and ‘Heterogeneous’ mixtures.