In “Flaming Bottle Rockets,” the latest video by The Royal Institution, host Andy Marmery demonstrates a science experiment that gives a large water jug forward thrust with a fiery ethanol-fueled burst.
The blue flame you see at first is a sign of complete combustion – when abundant oxygen reacts with the fuel, producing just the classic combustion products of carbon dioxide and water. As the oxygen supply is consumed, carbon particles start to be released, which cause the yellow flame. The pulses of flame that appear in the bottle towards the end of the reaction are probably created as fresh oxygen is drawn in from the top, and mixes with the remaining fuel.
The effect is even more pronounced when the footage is slowed down to demonstrate the different stages of the flame.
submitted via Laughing Squid Tips