Why Does Water Move on a Hot Surface Instead of Evaporating Immediately?

[The_Z_Factor]

I was boiling some water the other day in a pot and the stove was already hot, and a drop of water dripped from the pot onto the stove and it didnt evaporate or anything it just moved around all over the place until eventually about maybe 15-20 seconds later it "rolled" off the hot part of the stove and just evaporated or disappeared I am not exactly sure what happened.

So why does this happen? I mean, why does the water move the way it does over a hot surface, does something happen to those atoms in it so that when it comes in contact with heat they all just go crazy?

 

[russ_watters]

Surface tension holds it in a single dropplet while it is boiling away. And the heat and boiling makes it move around as it is boiling.

 

[Gokul43201]

If I understand the OP's scenario correctly, then what's happening is that the droplet is riding on a cushion of steam that forms as soon as the drop touches the overheated surface. The tiny layer of steam prevents direct contact between the droplet and the stove, keeping the droplet "alive" for several seconds. Sooner or later, the droplet loses balance (or the steam dissipates) and falls off the steam cushion, hits the surface, and boils away.

 

[noagname]

could this really happen for 15 to 20 seconds

 

[stewartcs]

Apparently so.

 

[Danger]

I've witnessed this a few times, but never thought to ask why it happened. Thanks for the input.

 

[pixel01]

I think the explanation of Gokul is correct. Steam or air has very low thermal conductivity so the droplet can survive quite a time. You can also see it jumping, because steam is created and expands suddenly making the droplet hover off the oven surface

 

[cesiumfrog]

By the way, it's known as the http://en.wikipedia.org/wiki/Leidenfrost_effect" effect.

 

[The_Z_Factor]

Ahh thank you everybody, and thanks cesiumfrog for the link, that pretty much sums it up.