Almost everything that we see around is matter. However, the question that arises here is whether the matter around us is pure or not? Moreover, How can we define the term purity? Many times we would have also come across sentences like, “water is pure” or “the milk used in making this tea is pure.” But is it correct to say this? Or what is the basis for saying that a substance is pure? Can we say any substance is pure if it is smooth or soft or it is white?
Pure And Impure Substances
To answers all these questions, as per the scientists, a substance is said to be pure if it is made up of only one kind of molecules or particles. Pure substances normally cannot be separated by simple physical methods and are largely classified as elements and compounds. An element consists of only one type of particles which can be atoms or molecules. Likewise, compounds can also be pure substances when they contain two or more elements which are combined in a fixed proportion by weight. In addition, pure compounds can be easily decomposed into separate elements with the help of suitable chemical methods.
A substance that is composed of different kind of elements or molecules then that substance is said to be impure. These types of substance are often referred to as mixture. Mixtures are further said to be either homogenous or heterogeneous. Mixtures are mostly made pure by the use of different types of separation techniques.
Characteristics of Pure Substance
- They are perfectly homogeneous in nature.
- They are made up of only one kind of atoms or molecules.
- They have a fixed composition.
- It has fixed density, melting point and boiling point etc.
Characteristics of Impure Substance
- It does not have any specific properties, the properties of the mixture are a result of the average properties of all the constituents.
- It is formed as a result of a physical change.
- They have a variable composition.
- The mixtures are homogeneous as well as Heterogeneous mixture in nature.
This was just a glimpse about the matter and its purity on the basis of its composition. Discover more about the topic here at BYJU’S.