Fire requires three things. Let's look at the combustion equation, the 'master of fire'.

Hydrocarbon (CxHx) + Oxygen (O₂) --heat--> carbon dioxide (CO₂) + Water(H₂0).

Let's examine the equation more closely: The first item is a hydrocarbon, also known as a combustible or, as you may commonly hear, a fuel. In the case of the experiment you noted, this can be in the form of the body of a match, the wick of a candle, or the butane in a lighter. Basically, you need fuel. The second item is oxygen, which was supplied in the balloon. The third item is heat, which initiates the reaction by supplying enough energy to overcome the barrier of the reaction.

This is the fire equation, and you need all three of these things for burning.

Firefighters will try to remove one of these ingredients to stop a runaway fire (Now do you understand why you have a fire blanket in your science classroom?). So, the oxygen does not burn on its own; rather, it needs a fuel. The more oxygen you have, the more intense the flame,because you are making the fuel the only limiting reagent. If the balloon was filled with air, you would only see a small flame nd not a' fireball,' because only about 1/5 of air is oxygen.

What you've done is heat up the air inside the bubble. This means that it exerts much more pressure on the bubble, and causes the bubble to expand, breaking the shell of liquid that is coherent around it in a spherical expansion.

This is because oxygen is very flammable and it bursts into flame very fast, so it keeps the shape of a ball for a short time.

In the space shuttle, flames are in the shapes of balls themselves, in the state free fall which the shuttle in orbit is in, which makes it seem as if there is no gravity.