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Fill a thin jar with boiling water (the water should be hot enough to the point that it is rapidly changing into water vapor).
The water will immediatly stop boiling due to the pressure compacting the molecules and increasing the boiling temp.
For those non-beleivers who beleive (heh, an oxymoron)that I have violated my own rules because the water is already boiling before the experiment starts:
(First of all, the expariment starts once I add the lid. Now for the explanation: Water normaly boils at 100 C and even if you add more energy, the temp of the water will stay at 100 C. Now taking that into concideration, if there is even the slightest amount of pressure, and the boiling point becomes 101 C, the water will immedietly stop boiling. so once you add the lid, pressure is immediately applyed and thus the water will imediatly stop boiling.
But, in order for this experiment to work, you must add more than enough energy to the water (in other words, continue heating the water even though it is already boiling) before adding it into the jar so that it will not immedietly stop boiling when only a bit of energy is lost (like when it touches cold air). That would imply that if you raise the boiling temp, the water should naturally gain heat till it matches the boiling temp. That assumption is wrong. The pressure will increse the boiling temp at a faster rate than the water will heat up so in fact, the water will not boil.)
(note: you are not decreasing or increasing the area in the glass jar so it is not in violation if the water vapor naturally applys pressure)
So, the temperature of the water is at the boiling point(with a regular air pressure) but the water is pressurized so it does not boil. Thus you see water that is not boiling in a jar. (you do have to add boiling water to the jar but it is only boiling before attaching the air tight lid, not after.)
Now to make the water boil:
If you seal the jar and rapidly take away heat (like pouring ice water on it), the water vapor should turn back into water thus redusing the pressure. So aslong as you have not taken away too much energy so that the water temperature goes below 100 degrees celsius, the air pressure should have reduced enough without so that the water can start boiling.
(note: although you transfered energy, you have not transfered energy into the jar; rather, you transfered energy out which is not in violation of the rules)
VOILA! Try it at home (it will take many trys though!)
An Idiot's Guide to Doing This Experiment:
Materials: a pot, a flask, water, ice, a heater
Steps: add water to the pot, heat the water till boiling, fill flask half way with boiling water, attach lid(or stopper), add ice to some cold tap water, slowly pour the cold water over the flask
Now it should boil for a few seconds. |
