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Q & A: leidenfrost effect

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Most recent answer: 08/06/2016
Q:
See http://physics.stackexchange.com/q/268650/102729) In Leidenfrost effect, the hot steam suspends water droplets above it and prevent the drop from touching the hot pan. My question is, as the steam is less denser than water, should the steam not travel up and make the water drop to touch the pan? You people are awesome. Continue the momentum.
- Deepak (age 23)
India
A:

Actually the explanations on that site sound reasonable. The drops of water are very close to the boiling point, so molecules are evaporating rapidly from their surfaces. That constant input of new vapor can keep the pressure up under the drop enough to keep it from contacting the metal even as the vapor keeps escaping flowing around the drop. The pressure on top, where the vapor can just flow directly away, is lower. If new vapor weren't being made, you're right that the drop would simply fall through the old vapor and contact the metal.

Mike W.


(published on 08/06/2016)

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