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Topic: Collapsing Can experiment...  (Read 8746 times)

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Byrne

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Collapsing Can experiment...
« on: January 06, 2006, 04:17:38 PM »
Basically what happens here is you empty the contents of an empty can of pop and fill it with some water.  Bring the water to a boil and then place the can in a bucket of ice and the can will collapse because the pressure within the can is now much less than outside the can

I have two questions:

Would this be a good demonstration during an Ideal Gas Law/Van der Waals equation demonstration?

Why does the pressure decrease when some of the water in the can condenses from steam to liquid after being placed in the ice?

Is it because the volume of gas decreases so, therefore, the pressure decreaes?

My goal here is to perform a calculation showing how the Ideal Gas Law and van der Waals Equation will yield similar results at normal pressures and temperatures.  So, if I were to be able to measure the volume of gas in the can after placing in ice condensed some of it into water, do you have to consider the water in the bottom of the can when finding your volume value?  This may be a stupid question, so forgive me if it is.

The other one we were considering was taking a piece of filter paper and sliding it overtop a flash filled with water and then inverting the flask to demonstrate the pressure of the air acting upwards is holding the water.

The problem is relating these experiments to the van der Waals equation... any ideas?

Thanks in advance
« Last Edit: January 06, 2006, 04:41:02 PM by Byrne »

GCT

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Re:Collapsing Can experiment...
« Reply #1 on: January 06, 2006, 11:24:12 PM »
Basically what happens here is you empty the contents of an empty can of pop and fill it with some water.  Bring the water to a boil and then place the can in a bucket of ice and the can will collapse because the pressure within the can is now much less than outside the can

I have two questions:

Would this be a good demonstration during an Ideal Gas Law/Van der Waals equation demonstration?

Why does the pressure decrease when some of the water in the can condenses from steam to liquid after being placed in the ice?

Is it because the volume of gas decreases so, therefore, the pressure decreaes?

My goal here is to perform a calculation showing how the Ideal Gas Law and van der Waals Equation will yield similar results at normal pressures and temperatures.  So, if I were to be able to measure the volume of gas in the can after placing in ice condensed some of it into water, do you have to consider the water in the bottom of the can when finding your volume value?  This may be a stupid question, so forgive me if it is.

The other one we were considering was taking a piece of filter paper and sliding it overtop a flash filled with water and then inverting the flask to demonstrate the pressure of the air acting upwards is holding the water.

The problem is relating these experiments to the van der Waals equation... any ideas?

Thanks in advance

So you were to boil the water in the can (I'm not sure if this is such a good idea, you may just want to heat it up a bit) and then somehow close up the can (a elastic polymer container with a lid seal may be better) somehow, the place it in the ice....yes this applies to van der waals equation.  You don't have to be exact, although the van der waals may be a better approximation it itself isn't adequate at times, if you simply wish to demonstrate the principle of things the ideal gas law will do.  So the temperature decreases, and if you were to assume a isolated system (no energy in or out), then you would have a net decrease in volume.

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Re:Collapsing Can experiment...
« Reply #2 on: January 07, 2006, 05:04:05 AM »
This deals with a phase change from gas to liquid. Its more complicated than just applying the ideal gas law.
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Byrne

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Re:Collapsing Can experiment...
« Reply #3 on: January 07, 2006, 01:25:03 PM »
This deals with a phase change from gas to liquid. Its more complicated than just applying the ideal gas law.

My goal here is to perform a demonstration that in some way applies to the van der Waals equation...

Chrataxe

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Re:Collapsing Can experiment...
« Reply #4 on: January 07, 2006, 02:49:16 PM »
Basically what happens here is you empty the contents of an empty can of pop and fill it with some water.  Bring the water to a boil and then place the can in a bucket of ice and the can will collapse because the pressure within the can is now much less than outside the can

Th pressure is lower outside the can?

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