The temperature of the surface is so hot that water droplets bounce and dance.
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Theory
Since the hot plate is is held at a temperature much higher than the boiling point of water, the droplets boil instantly when they fall. A small layer of steam forms in between the droplet and the plate resulting in motion similar to that of a hovercraft. The droplet can "skate" around on this cushion of steam for some time before it completely boils off. This effect only happens when a surface exceeds the boiling point of a liquid by a large amount.
Apparatus
- hot plate
- cup of water
- large pyrex beaker of water
Procedure
- Place the large pyrex beaker of water onto the hot plate. The beaker will help to regulate the temperature of the hot plate.
- Turn on the plate and heat it up as you would to bring the beaker to a near-boil.
- Drip some water carefully onto an exposed area of the plate. If the temperature is hot enough, the water droplets should dance about.
Safety
- Be very careful using water around electrical devices.
- Drip the water onto the plate is VERY small amounts. Too much water can lead to the water "exploding", potentially burning your hands or face.
- Be careful to protect yourself against burns from the produced steam.