Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] two fluids questions



On the other hand, purely from anecdotal evidence, if a cap a half bottle of beer and return it to the fridge, versus leaving the bottle uncapped - I taste no difference in the carbonation of the beer after a day or two. (My body can't handle more than a half bottle at a time) The only advantage to capping it appears to be keeping out unwanted flavors. I first noticed this with soda - like Pepsi. The temperature the soda is kept at seems to be much more important than if the cap is placed back on the bottle.

Bob at PC

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of curtis osterhoudt
Sent: Thursday, November 18, 2010 1:38 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] two fluids questions

1. I suspect your chemistry colleague is simply wrong. Taken to the
extreme, his
argument that the CO2's partial pressure won't change would indicate
the same
result whether there's a vacuum above the fizzy drink, or a pure CO2
atmosphere.
The suggestion to preserve the fizz by removing the air is absolutely
tosh.

2. The pressure *does* go up; by changing the pressures in parts of the
bottle,
one allows CO2 to come out of solution, which of course increases the
volume it
takes up. But, given time (and room temperature), the equilibrium is
restored,
as you posit. It may not be quite back at the starting point (same
concentration
of gases in the fluid; same head pressure, etc.) but it will be pretty
close.


/**************************************
"The four points of the compass be logic, knowledge, wisdom and the
unknown.
Some do bow in that final direction. Others advance upon it. To bow
before the
one is to lose sight of the three. I may submit to the unknown, but
never to the
unknowable." ~~Roger Zelazny, in "Lord of Light"
***************************************/




________________________________
From: Anthony Lapinski <Anthony_Lapinski@pds.org>
To: phys-l@carnot.physics.buffalo.edu
Sent: Thu, November 18, 2010 11:18:09 AM
Subject: [Phys-l] two fluids questions

1. You may have seen a Fizz-Keeper sold in supermarkets. It's a plastic
attachment you screw onto a plastic soda bottle. You pump it to force
air
into the bottle. This creates a higher air pressure above the soda, so
it
should preserve the soda from going flat. Makes sense. However, my
chemistry colleague recently informed me that this does not work! He
said
the partial pressure of CO2 will be the same whether you increase the
air
pressure or simply put the cap on. The best way to preserve the fizz
would
be to add CO2 gas, or simply squeeze the bottle to remove most of the
air
and then cap it. Does this make sense? I know physics, but not as much
chemistry.

2. If you shake a plastic bottle of unopened soda, the inside pressure
should remain the same since it is a closed system. But if you then
squeeze the bottle, it certainly feels like the pressure has increased.
Is
this a temporary thing until equilibrium is established after some
time?

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l




_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l