THERMODYNAMICS - CHANGE OF STATE - PHASE CHANGES: LIQUID-SOLID	Order
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Description: A beaker contains liquid nitrogen. Pump out the bell jar to freeze the liquid nitrogen. The freezing temperature is about 68 degrees Kelvin, about ten degrees below the liquefying temperature of 77. Only the surface may freeze and then break as pumping continues. Setup Time: 10 min Quant. in Demo Room: 1 Demo References Sutton H-109 Pumping on liquid air will produce solid nitrogen at -210 C. Air passed slowly over the outside of the flask will condense out liquid air at atmosphere pressure. The American Journal of Physics AJP 35(6),540 In addition to the standard freezing by evaporation in a clear dewar - pop off the cork when the nitrogen is solid and it will instantly turn to liquid while the temperature remains below its boiling point.
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