Here's a fine demo on how fire needs and seeks oxygen. Or a magic trick, ;), if you prefer.
You'll need two matches (or one match and a lighter), a wine glass or small glass, a bit of colored water, a heavy coin, and a shallow dish.Bend your match a bit near the end.
Place a coin over the bent end to stand it upright.
Pour your colored water into you dish.
Ignite your match with another, or a lighter
place your wine glass over the match.
The match - even after it's burned- draws in the water, providing suction.Cool.
This idea came from here.