Mixtures and Its Types

An impure substance, or a mixture, contains two or more substances in any proportion. Also, these substances can be separated from one another. A mixture may contain elements, compounds, or elements and compounds. A mixture should not be confused with a compound. The proportion of the constituent elements in a compound is fixed. But that of the components of a mixture is not. 

For example, any amount of salt or sugar can be mixed with any amount of water to form a mixture.

Most materials that we use or come across are mixtures. Some of them are useful and others need purification (i.e., separation) before use.

1.0Characteristics of Mixtures

(1) A mixture may be homogeneous or heterogeneous.

(2) The constituents of a mixture can be separated by physical means like filtration, evaporation, sublimation and magnetic separation.

(3) In the preparation of a mixture energy is neither evolved nor absorbed.

(4) A mixture has no definite melting point and boiling point.

(5) The constituents of a mixture retain their original set of properties. For example, magnet attracts iron fillings in a mixture of sand and iron fillings.

2.0Types of Mixture

Depending upon the nature of components, a mixture can be divided into two types.

Homogeneous Mixture

A mixture in which different constituents are mixed uniformly, is called a homogeneous mixture. This mixture has same composition throughout. Homogeneous mixtures are also known as solutions. The components of such a mixture cannot be seen even under a microscope. e.g. salt solution, sugar solution. Similarly alloys such as brass, bronze etc. are homogeneous solid solutions of metals. 

Heterogeneous mixture

A mixture in which different constituents are not mixed uniformly, is called a heterogeneous mixture. The components of a heterogeneous mixture can be observed with naked eyes or with the help of a microscope. This mixture has different composition in different parts e.g. Sand and iron filings, sand & water etc.

Some examples of naturally occurring and man-made useful mixtures are given below.

(1) Air 

Air contains the elements nitrogen, oxygen and argon and the compounds carbon dioxide and moisture (water vapour).

(2) Natural water 

Natural water contains dissolved air, which is essential for aquatic animals. 

(3) Sugar solution and soft drinks 

A solution of sugar or glucose in water is a mixture. Soft drinks (or fizzy drinks) contain carbon dioxide dissolved in water, to which are added some sweetening and flavouring agents. They are highly refreshing.

(4) Medicines

Most medicines are mixtures. On the label of a medicine bottle, you will find the substances or ingredients it contains.

(5) Alloys 

An alloy is a metal mixed with other metal(s) or non-metal(s). The components are so thoroughly mixed that the whole thing appears to be a single substance. They are usually made by melting the components together and allowing the melt to solidify. Alloys are generally stronger than the metals they contain.

Steel, the most common alloy, contains iron with small amounts of carbon and manganese, Stainless steel is a special steel containing some chromium and nickel also.

Brass contains copper and zinc, whereas bronze contains copper and tin. Pure gold is not suitable for making jewellery. Pure gold is soft and gets reshaped by small pressures. So, the gold used for making jewellery is made stronger by alloying it with silver and copper.

3.0Also Read