Question

how will you prove that air is needed to burn a material

Answer 1

For burning oxygen is required.Without oxygen the burning will not happen. So the air is needed to burn a material. Air is a mixture of many gases.

Answer 2

Combustion or burning of substances can happen only in the presence of oxygen, which is abundant in the air (an approx. value of 21 percent in the atmosphere).
To prove the same...
Keep a lighted candle. Cover it with a glass tumbler.
The flame will continue burning until oxygen is present in those close quarters.
After a while, the flame will go off.

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