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Leidenfrost Effect PDF Print E-mail
 
 

Description:

Filmed with a high speed camera, this video shows how droplets of liquid nitrogen behave when poured on a warm surface like the floor.


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Possible Incorporated Topics:

  • Phase Transitions
  • Boiling Point


Theory:

 

    Liquid nitrogen is extremely cold and has a boiling point of approximately -196 C. This means that the floor in the physics lab, or in just about any room for that matter, is way hotter than the boiling point of liquid nitrogen. In fact, it is so much hotter than the boiling point of liquid nitrogen that when they come in contact, a phenomenon known as the Leidenfrost effect occurs. With this effect it seems as though the liquid is skating or gliding across the surface with little to no friction. 

 

 

    Since the floor is so much hotter than the boiling point, the droplets of liquid nitrogen boil instantly when they touch it. When this happens a small layer of nitrogen gas forms in between the droplet and the floor resulting in motion similar to that of a hovercraft. The droplet can "skate" around on this cushion of gas for some time before it boils up. This effect only happens when a surface exceeds the boiling point of a liquid by a large amount. It can also be seen when small amounts of water are tossed in a hot frying pan.

 


Apparatus:

  • Liquid nitrogen

  • A large surface at room temperature

 

Procedure: 

  1. Carefully pour the liquid nitrogen on the surface and observe the Leidenfrost effect in action.

 


Safety:
  • Be very careful when using liquid nitrogen, wear safety goggles. Don't let it touch you or your clothes.
  • The liquid nitrogen will spread out pretty quickly, be cautious of where you do it and make sure nobody is too close to where the nitrogen is being poured.
  • Don't pour too much liquid nitrogen in one place on certain floors or you will risk ruining the flooring material.