Question

justify the air is a mixture of gasses

Answer 1

yes air is a mixture of gases as it constituets many different gases like
78.09% nitrogen, 20.95% oxygen, 0.93%argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

and thus its proved air is a mixture of many gases....

hope this helps.....:)

Answer 2

The mixture of their changes from place to place and from time to time the percentage of oxygen becomes lesser and lesser as you go higher and higher therefore hence Mountaineers Carry oxygen cylinders while climbing so the slightly heavier oxygen is found more in the plains than at higher altitude the composition of oxygen is not same it varies from place to place the different components of air retain their identity