Why is air called a mixture ? Give five facts in support of your answer.

Air is called a mixture because it is made up of several different gases, dust particles, water vapour, smoke and other impurities that are physically combined, not chemically bonded.

Five facts which show that air is a mixture :

1. The composition of air varies from place to place and from time to time.
2. No energy change occurs when the components of air are mixed together.
3. The components of air retain their individual properties.
4. Air cannot be represented by a formula as its constituents are not in a fixed proportion.
5. The components of air can be separated by simple physical methods.