Hovercraft

Place a tin lid on a hot plate and heat it well (take care!). If you then let a few drops of water fall on the lid, you will observe a small natural phenomenon. The drops are suspended in the air like hovercraft and whiz hissing to-and-fro for a while.

On contact with the heated metal the water drops begin to evaporate at once on the underside. Since the steam escapes with great pressure, it lifts the drops into the air. So much heat is removed from the drops by the formation of steam that they do not even boil.