I need some SCIENCE!

[Peelee]

How much of air is O2?
Take a tea-light candle, float it in a bowl of water then light it.
Now put a clear glass upside-down over the candle (it needs to not seal with the bottom of the bowl)
Watch as the water level in the bowl goes up as the O2 is used up before the candle goes out.

I would expect the opposite effect for various reasons.

I would expect zero effect, since water is incompressible, so the water level certainly shouldn't go down, and heating the rest of the gas expands it. Even if the gas doesn't expand the gas enough, the lower the pressure, the faster the water will evaporate. So yeah, I'd expect either no change in water level or (very minimal) lower water level.

Of course, what I'd expect and what actually would happen are not necessarily correlated.