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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.
Procedure:Fill the condenser on the vacuum pump with liquid nitrogen to prevent water vapor from entering the pump. Turn the pump on and the water will begin to boil
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.
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