pure substance. A mixture contains many types of particles. A mixture contains particles of two or more pure substances which may be present in it in any ratio. Hence, their composition is variable.
Pure substances forming mixture are called its components. Many of the substances present around you are mixtures . For example, sugar solution in water, air, tea, etc., are all mixtures. A mixture may be homogeneous or heterogeneous .
In a homogeneous mixture , the components Fig. . Classification of matter Fig. .
Arrangement of particles in solid, liquid and gaseous state completely mix with each other. This means particles of components of the mixture are uniformly distributed throughout the bulk of the mixture and its composition is uniform throughout. Sugar solution and air are the examples of homogeneous mixtures. In contrast to this, in a heterogeneous mixture , the composition is not uniform throughout and sometimes different components are visible.
For example, mixtures of salt and sugar, grains and pulses along with some dirt (often stone pieces), are heterogeneous mixtures. You can think of many more examples of mixtures which you come across in the daily life. It is worthwhile to mention here that the components of a mixture can be separated by using physical methods, such as simple hand-picking, filtration, crystallisation, distillation, etc. Pure substances have characteristics different from mixtures.
Constituent particles of pure substances have fixed composition. Copper, silver, gold, water and glucose are some examples of pure substances. Glucose contains carbon, hydrogen and oxygen in a fixed ratio and its particles are of same composition. Hence, like all other pure substances, glucose has a fixed composition.
Also, its constituents—carbon, hydrogen and oxygen—cannot be separated by simple physical methods. Pure substances can further be classified into elements and compounds . Particles of an element consist of only one type of atoms. These particles may exist as atoms or molecules .
You may be familiar with atoms and molecules from the previous classes; however, you will be studying about them in detail in Unit . Sodium, copper, silver, hydrogen, oxygen, etc., are some examples of