Description:
Frost forms on the outside of a cup filled with liquid nitrogen.
Watch Video:
Other Demos of Interest:
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|
Leidenfrost Effect |
Dry Ice Bubbles |
Exploding Erasers with Nitrogen |
Possible Incorporated Topics:
- humidity
- crystallization
- water vapour
- freezing point
Theory:
Frost is made up branches of ice crystals that form in the cold if the air is humid. Humid air is full of water vapour. When a cup is filled with liquid nitrogen, it becomes cooled below the freezing point of water (0*C). This causes the water in the humid air to crystallise on the surface of the cup, forming frost. As the liquid nitrogen is warmed by the surrounding air, it boils off. Once the nitrogen boils off the frost melts as it is no longer being cooled to below its freezing point.
Apparatus:
- styrofoam cup (coloured blue for contrast)
- liquid nitrogen (including proper safety attire: safety glasses and cryogenic gloves)
- Note: for best results, do this on a humid day!
Procedure:
- fill styrofoam cup with liquid nitrogen
- frost will form on the outside of the cup
- once the liquid nitrogen has boiled off, the frost will melt
