Air is a mixture, but not a compound. Explain why?

Hint:‌When two or more substances (elements or compounds) are mixed together in any proportion it is called as a mixture. A pure substance, which is composed of two or more different elements, combined chemically in definite ratio is called a compound.

Complete step by step answer:
We know that, in a mixture, constituent substances retain all of their individual properties. Mixtures can be separated by simple physical methods. On the other hand, in compounds, constituent elements lose their individual properties and these elements can be separated only by chemical methods. Compositions of mixture are not same throughout but compounds have a homogeneous composition i.e. it is same throughout.
We are surrounded via air from all over and the composition of this air isn't the equivalent all over. The level of oxygen diminishes at higher elevations. Likewise, in mechanical territories level of carbon dioxide and other contaminating gases increments. Main components of air can be separated by simple physical processes such as liquefaction and fractional distillation. When constituents of air are mixed, minimal reactions occur between them which can be neglected i.e. no energy is evolved or absorbed when components of air are mixed. Each constituent of air retains its physical and chemical properties. For example, Oxygen supports combustion. Carbon dioxide turns lime water milky.
Hence, air is a mixture.

Note:The major difference between mixture and compound is that the composition of compound is same throughout but it’s not the case for a mixture. Air also follows other properties of a mixture.