Dancing Droplets of water experiments (Leidenfrost Effect)

Why does a droplet of water not boil off immediately when we put it on a super hot pan?
When the pan surface is clean and very hot the water underneath the droplet boils instantly and create a thin layer of steam under the drop. This layer of steam insulates the cold water from the hot pan and the hot pan from the cold water, the heat transfer is reduced considerably.

 

A tiny graphic pops up for a very short time that illustrates this leidenfrost effect, if you blink you miss it.

 

The underlying physics of the effect? Water has a strong surface tension due to hydrogen bonding and can hold together in a droplet which is very stable.

 

Be careful if you do this experiment some drops can superheat and explode rarther than float like a hovercraft

 

This is due to something called “Leidenfrost effect”.
Basically when the pan is very hot, if you drop a droplet of water, a small layer thickness of water vaporises quickly and form a insulating layer. This insulating layer results in lower rate of heat transfer to rest of the water drop and the water drop floats on the vaporised layer.

 

The pan is actually hotter when the drop floats rather than when the whole drop vaporises. (The protective vapor layer is not formed if the pan is not very hot). This is a beautiful counter intuitive experience.

 

No Comment

Post A Comment

error: Context Menu disabled!