Air can be classified under

A mixture is a material, which consists of two or more pure substances (elements or compounds) which are not chemically combined but physically mixed in any proportion. A mixture shows the properties of all its constituents and it can be reported into its constituents by physical method. Air is a homogeneous mixture of many gases like nitrogen (78%), oxygen (21%), carbon dioxide, inert gases and water vapours. Air is a mixture because its properties are in between those of its constituents. The two major components of air are oxygen and nitrogen. In the presence of oxygen, any fuel burns brightly but in nitrogen it gets extinguished. In contrast, in air, the fuel burns slowly. The components of air can be separated by fractional distillation; moreover the composition of air is also variable. Thus, air is a mixture. An element is a pure substance that contains only one kind of atoms. A molecule is a group of two or more atoms, which are held together strongly by some kind of attractive force. For e.g. H₂, Cl₂, Br₂, etc. A compound is made up of two or more elements chemically combined in fixed proportion by mass. For e.g. H₂O, HCl, NH₃, etc.