What is Leidenfrost Effect?
It is so-called after Mr. Johann Gottlob Leidenfrost, who did research on it in 1976. This effect usually occurs when a liquid is brought close to a surface which is much hotter than that liquids boiling point. If this happens, there is production of a layer of vapor that insulates the specific liquid by physically separating it from the hot surface it was put on. The vapor found between the hot surface and the liquid prevents contact between the two thus referred to as Leidenfrost effect..
The Leidenfrost Effect
This effect usually takes place when one heats up a burner and then sprinkles some water on it. If the pan is very hot, those water droplets usually skitter away from the area of contact. That is the Leidenfrost effect taking place. It can also be easily demonstrated by spilling a little amount of liquid nitrogen onto the surface. Liquid nitrogen’s boiling point is -195 degrees Celsius. The drops skitter on the surface like that of water.. Another illustration would be the elucidation of how people are able to walk over hot coal. They usually do this after dipping their legs on water. The surface of hot coal is at a higher temperature than that of the boiling point of water thus protecting the legs of the person walking over it through Leidenfrost effect.
The Leidenfrost Point
This is the temperature at which the Leidenfrost effect occurs. It’s not easy to recognize the precise temperature that this takes place. If a liquid is placed on a surface that is cooler than its boiling point then the liquid flattens out and heats up. When the surface is at boiling point, the liquid usually hisses but then flattens and boils into vapor. But when the surface is at a higher hotness than boiling point the liquid has, Leidenfrost effect takes place. It usually depends on factors like the volume of liquid placed, atmospheric pressure, and the properties of the surface one is using. The Leidenfrost effect for water is about 200 degrees Celsius but this can’t predict that of other liquids..
- Anne Marie Helmenstine, Ph.D. “Leidenfrost Effect Demonstrations.” n.d. About.com Website. Document. 18 05 2014.
- Leidenfrost, Johann Gottlob,. “On the Fixation of Water in Diverse.” International Journal of Heat and Mass Transfer (1966): 1153-1166. Document.