# Physics of H20 / vapor / Leidenfrost Effect in kettle **URL:** \ **Category:** Factual Questions\ **Tags:** science-math\ **Created:** [February 6, 2024, 5:30pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195 "2024-02-06T17:30:32Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [February 6, 2024, 5:30pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195/1 "2024-02-06T17:30:32Z")
Hi there, random shower thought: when you boil water in an (e.g.) electric kettle - you will see air bubbles rising at the end of the boiling process (rolling boil?) I assume the gas bubbles come from the Leidenfrost effect, and are - hencly - water vapor … [![](https://img.youtube.com/vi/HVgxpZmP51o/maxresdefault.jpg "Boiling water in a clear glass kettle") ](https://www.youtube.com/watch?v=HVgxpZmP51o) My Q is now the following: what happens physically there? … is the H20 (a liquid) broken up into H2 and O (two gases)? If I do this on a greater scale in a small space (e.g. bathroom) … would the O concentration in the air increase (assuming sealed space)? Could I - theoretically - replace the atmosphere in the bathroom with H2 and O (would the air pressure increase, as the atmosphere is not consumed?) - if I scrub the atmosphere? thx for following me on this mental exercise (w/ lots of stupid thoughts)… ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [February 6, 2024, 5:40pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195/2 "2024-02-06T17:40:58Z")
If you heat up a bunch of water (heat of vaporization) it will turn into a gas, but not disintegrate. If you need some oxygen, you can use an [oxygen concentrator](https://en.wikipedia.org/wiki/Oxygen_concentrator), but too much oxygen in a room could be dangerous… > [@Al128](#): > > Could I - theoretically - replace the atmosphere in the bathroom with H2 and O > [@mixdenny](#): > > If you put two wires into the water and run a DC current though the water the water will split into H and O ions, and bubble from the two wires. Now you have H and O. Add an ignition source and Bang, water again. You could fill a room with such a mixture, but that is also a bad idea 🙂 ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [February 6, 2024, 5:44pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195/3 "2024-02-06T17:44:39Z")
The bubbles of air are just a physical change, not a chemical change. All that is happening is that a “hot spot” has concentrated a bit too much heat and the water at that spot has boiled. It’s still H2O. If you put two wires into the water and run a DC current though the water the water will split into H and O ions, and bubble from the two wires. Now you have H and O. Add an ignition source and Bang, water again. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [February 6, 2024, 9:21pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195/4 "2024-02-06T21:21:59Z")
> [@Al128](#): > > what happens physically there? … is the H20 (a liquid) broken up into H2 and O (two gases)? [Boiling](https://en.wikipedia.org/wiki/Boiling) is merely the physical change whereby a substance is rapidly changed from its liquid to its gaseous state. Ice is solid water. Water also has its familiar liquid form. And water vapor is gaseous water. All are H2O. Dissociating the water into its constituent elements is a very different thing. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [February 7, 2024, 4:12pm UTC](https://boards.straightdope.com/t/physics-of-h20-vapor-leidenfrost-effect-in-kettle/997195/5 "2024-02-07T16:12:17Z")
OK, if you heat the water to 3000–4000 degrees (hard to do with a glass kettle) then thermodynamic equilibrium will indeed result in significant concentrations of OH, H, H₂, O, and O₂. At 3500K and 1 atmosphere over 50% of the water molecules will be dissociated. Then you will need to cool and extract your products quickly, before they can recombine.