If we look around us, we find that almost all the matter around us is made up of two or more pure components. What are these substances called? These are the mixtures. So, a mixture is a substance that contains two or more pure substances which are not chemically combined but mixed physically in any proportion.

For example, Air is a mixture of gases. Similarly, milk, ghee, oil, and spices such as garam masala are all mixtures, containing particles of different types. We can, therefore, conclude that matter around us is broadly categorized into two types. They are either Pure Substances or are Mixtures.

Have you ever noticed the word �pure� written on some consumables? You must have. But when is a substance considered pure? A substance is considered pure when all its constituent particles are the same in their chemical nature. Pure substances are the ones in which all the constituent particles are the same in their chemical nature.

Table sugar, salt, and aluminum foil are examples of pure substances containing only one type of particle. We must note that in nature, almost no substance is pure and pure substances are made such by humans by separating out the unwanted substances.

On the other hand, a mixture is a substance that contains two or more pure substances which are not chemically combined but mixed physically in any proportion.

Depending upon the nature of the components that form a mixture, mixtures can be broadly classified into two types namely:

1. Homogeneous mixtures
2. Heterogeneous mixtures

Let us now discuss the two types of mixtures one by one.

What is homogeneous mixture?

Homogeneous mixtures: These are the mixtures that possess a uniform composition throughout. The components of such a mixture are not visible to the naked eye or even under a microscope. The composition, however, can vary. Homogeneous mixtures in which at least one component is a liquid are called solutions. The salt solution in water is an example. Among the gases, the air is a well-known example of homogeneous mixtures. Similarly, in solids, alloys are examples of such mixtures.

What is heterogeneous mixture?

Heterogeneous mixtures are the ones that possess visibly distinct parts or phases and have non-uniform compositions. Unlike homogeneous mixtures, the components of a heterogeneous mixture are either visible to the naked eye or under the microscope.

A mixture of oil and water, salt and sulfur, copper sulfate and potassium permanganate, etc. are some examples of heterogeneous mixtures.

Various properties of mixtures are:

� A mixture may be homogeneous or heterogeneous.
� The composition of a mixture may be variable.
� Mixtures generally do not possess definite formulae or other physical properties such as melting point or boiling point.
� Components of a mixture are not chemically combined. Therefore, there is no change in energy during the formation of a mixture.
� Usually, the constituents of a mixture can be separated by simple physical methods.