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Quick Question About Plastic Bottle Delfating!

by QuantamMan
Tags: bottle, delfating, plastic
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QuantamMan
#1
Nov28-10, 08:05 PM
P: 3
Hi Guys,

I am new here, but I have a quick question.
I had a somewhat tepid liquid in a plastic soda plastic 2L bottle
When I tightened the cap to close it all was well and normal
After a day a portion of the top of the bottle deflated, as if oxygen was sucked out

Can someone explain this process?

Thank You
QM
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omoplata
#2
Nov28-10, 08:12 PM
P: 315
Was the water warmer than room temperature?

If yes, the temperature of the bottle and the water became equal after you closed the cap. The air volume contracted as its temperature went down. It couldn't get air from outside because the cap was closed.

http://en.wikipedia.org/wiki/Thermal_expansion
QuantamMan
#3
Nov28-10, 08:23 PM
P: 3
Quote Quote by omoplata View Post
Was the water warmer than room temperature?
yes, we have been having snowfall lately, it's cold right now

omoplata
#4
Nov28-10, 10:01 PM
P: 315
Quick Question About Plastic Bottle Delfating!

Here is a clearer and more correct explanation.

Let's assume when you closed the cap, the bottle, the air inside it, and the soda were at the same temperature. When you closed the cap, matter (air) couldn't move in or out of the bottle, so you made it a Closed System. There was Heat Conduction between the liquid and air mixture and the outside air through the bottle. So the soda and air mixture which was at a higher temperature than the room transferred heat out to the air in the room until it was at the same temperature as the room. But the volume of a certain substance depends on it's temperature: Thermal Expansion. So they reduced in volume. But air and water (~soda) have different Volumetric Thermal Expansion Coefficients. So air contracted more as the temperature reduced. That's why the soda volume seemed to be the same but the air volume appeared to be less.

You can look up these terms in your science textbooks too.


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