Leidenfrost Effect

A drop of water on a hot surface, illustrating the Leidenfrost effect
Cryonic07 / CC BY-SA

In 1756, Leidenfrost observed that a droplet of water deposited on a hot surface does not instantly vaporise, but remains a droplet for a considerable duration of time and slides freely around the surface. This is known as the Leidenfrost effect, as we discussed here.

The two videos below, from Vakarelski et al, show (respectively) the break-up of a Leidenfrost layer and a race between falling spheres.

We have harnessed the Leidenfrost effect to create a sublimation heat engine, which you can read about here.