Hiw will you prove that air is needed to burn a material
Answers
It isn’t. Yes, you heard me right; you don’t need air to burn something.
What you need is an oxidizer. Fuel plus oxidizer equals rapid redox reaction, aka “combustion”. For proof, you just need a vacuum chamber, in which you have something to use as fuel (this can be a traditional fuel like wood, or something more exotic, maybe something you wouldn’t think would burn, like, say, sand), and a few drops of a lovely little chemical called chlorine trifluoride. With a dropper or pipette (oh, make sure the pipette is made of a high-nickel metal alloy), put a drop of the ClF3 on the fuel of choice and watch the fireworks.
Now, chlorine trifluoride is fairly exotic, though if you work in the semiconductor industry you’ll be pretty familiar with it. By far the most plentiful oxidizer on Earth is… oxygen. It’s the second most powerful oxidizing element after fluorine, and it comprises about 18% of our atmosphere. So, it’s readily available in pretty much any space where humans can also exist without specialized equipment.