Why do water drops dance when poured on a hot plate?

    When a drop of water (at room temperature, 30 degrees centigrade) falls on a hot plate (at a temperature of say 150-200 degrees centigrade), the water begins to ‘dance’ around on the plate because of the formation of a layer of steam, at the interface of the drop and the late, which acts as a cushion. When the drop touches the plate, the bottom layer of water in the drop is suddenly heated to more than 100 degrees centigrade leading to the formation of steam at the interface.

            Steam not being a good conductor of heat, does not allow the plate’s heat to flow easily into the drop. So, as we move up from that interface, into the drop, the temperature falls down.

            The layer immediately above the steam will be of boiling water. In the outer top layer, called the free convection zone, water is heated slightly. At any point of time, the water tries to rest on the plate but the steam holds it up by acting like a cushion.

            As a part f the steam leaks out sideways, certain amount of water flows in to fill gap and gets vaporized. This process continues till the water drop is completely vaporized or the hot plate is cooled to below 100 degrees centigrade.