We had a summer rain shower yesterday. Afterwards I could see steam rising off the street as the water evaporated. I could walk barefoot on that street before the shower and while the water was evaporating. If the water was boiling away, surely I wouldn’t be able to walk across it without scalding my foot.
What’s going on here?
In: Planetary Science
Temperature is the *average* speed of particles in a material. There’s a whole distribution of speeds and at any time *some* of them are going fast enough to fly out from the surface (aka evaporate) even if the *average* speed of the whole group is not fast enough to do this.
Note that even ice in the freezer shrinks over time – proving that even below 0C, at least some small fraction of water molecules are still bouncing fast enough to escape. Even when the average speed of the molecules in the whole cube is below 0, way below boiling point!
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