How Does a Candle Burn Without Oxygen?

Imagine lighting a candle, it glows, and you can see the flame. Now imagine putting a glass jar over it. At first, the flame gets smaller, but then poof! The flame goes out, but if you wait a little, it comes back to life. It looks like it’s burning without oxygen. But how? Well, when the candle burns, it uses up the oxygen inside the jar, that’s why the flame gets smaller. But then the wax starts to change into something else called carbon dioxide, which is like a new gas in the jar. When there's enough of this new gas, it helps the flame burn again, even though there’s no more oxygen.