→ Air is a mixture of different gases.
→ Air contains oxygen which is essential to living organisms for respiration. So it is called breath of

Role of Atmosphere
→ Air is a bad conductor of heat. It keeps the average temperature of the earth constant during th
day and even during the course of the whole year.
→ Prevents the sudden increase in temperature during day time and during the night, it slows dow
the escape of heat into outer space. 
Example: At moon, there is no atmosphere and so the temperature varies from 190ºC to 110ºC.