Show Me Some Science! Liquid Oxygen Flaming Pretzels

 In Show Me Some Science

Liquid oxygen is collected on a pretzel, and when lit it burns like a Roman Candle!

Where does the oxygen come from?

The air is about 78% Nitrogen. Liquid Nitrogen, the frosty looking stuff in the video, is essentially liquid air. It’s really cool — literally! About 77 Kelvin or −321 °F. In fact, it’s so cold that if you put it in a container, oxygen will condense on the sides, similar to water condensing on the outside of a glass of ice water. Oxygen becomes a liquid at a higher temperature, (90.19 K  or −297.33 °F) so this makes sense!

Why does the pretzel burn like that?

Burning is a chemical reaction (oxidation) that requires 3 things: heat, fuel and oxygen. Usually, a pretzel burns much slower because it uses oxygen from the air, and there’s only so much surface area that is in contact with the oxygen. We saturated the pretzel with liquid oxygen, so it’s able to get oxygen more quickly and thus burns much faster!

Flaming Pretzel