Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538
Demonstrations are cataloged according to PIRA Bibliography
PLEASE REQUEST DEMOS WELL IN ADVANCE
Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.
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You have selected the following Demos:
video - Boiling by Reducing Pressure
Purpose:To show that the boiling point of a liquid, in this case water, depends on pressure as well as temperature.
Fill the cold trap on the vacuum pump inlet port with liquid nitrogen (LN2) to prevent water vapor from entering the pump and spoiling the oil. Turn ON the pump and the water will begin to boil once the pressure drops close to vacuum.
Hints:You might want to move the vacuum chamber off the pump cart to avoid the vibrations of the water beaker. This way the water disturbance due to boiling is more sudden and dramatic.
Few neat tricks can be demonstrated.The lecturer can pressurize the chamber quickly and pull the beaker out to stick the finger into "boiling" water.
Continuous pumping is actually cooling by evaporation and the water actually keeps getting colder. This can be demonstrated by measuring the temperature of water before and immediately after the pumping.