Date: Tue Feb 20 13:03:37 2007

Author: Richard Berg

Subject: Re: CO2 release from soda

Post:

I believe this is why water can be superheated more easily in a smooth cup
or beaker than in a cup with a really rough surface.

http://www.phys.unsw.edu.au/%7Ejw/superheating.html

Dick

On Tue, 20 Feb 2007, Bernard Cleyet wrote:

> Solubility of gasses in liquids usually decreases w/ temperature, therefore,
> I don't think that (paragraph 1) is the reason. I'm rather certain the ice
> supplies nucleation points for the concentration of the CO2 into bubbles;
> the same reason for the infamous mentos demo.
>
> Diluting soda w water (paragraph 2) will reduce bubbling because it reduces
> the CO2 concentration, however, if the water is not pure and air free, it
> will supply nucleation sites and have the opposite effect.
>
> bc, waiting to see if incorrect. [doesn't believe in PBBA)
>
> p.s. this has been a discussion on another list, perhaps I'll question it.
> (paragraph 3)
>
> p.p.s. first response to googling:
>
>
> http://www.physlink.com/Education/AskExperts/ae441.cfm
>
> constitutes PBATA (os should I write G?)
>
> Papp, James J wrote:
>
>> I thought that the solubility of the CO2 gas in water was a function of
>> temperature as well as pressure, so that the cooler water-gas mixture
>> would expel the gas more quickly. Rather than the walls weakening, the
>> gas pressure in the bubbles increases as the rate of gas flux increases.
>>
>> I will go ahead and say that I was under the impression that the flat
>> soda was the result of melting ice diluting the CO2-water mixture,
>> reducing the gas pressure of the CO2 in the new mixture.
>>
>> If anyone has better information, or has a chemist on hand who could set
>> us (ok, me) straight, please do it. I would like to see some numbers on
>> this - I remember working problems with partial gas pressure in
>> chemistry, but I have not the resources on hand to reproduce them.
>>
>> Thanks,
>>
>> Jim Papp
>>
>> -----Original Message-----
>> From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
>> Behalf Of cablem
>> Sent: Tuesday, February 20, 2007 10:31 AM
>> To: tap-l@lists.ncsu.edu
>> Subject: [tap-l] CO2 release from soda
>>
>>
> cut
>
>> My guess is the rapid cooling somehow weakens the walls of the bubbles,
>> thus allowing them to pop and release the gas. In fact, I'm willing to
>> bet that any abrupt change in temp causes the bubbles to do this. Pour
>> some soda onto a hot skillet and see what happens. Be safe while you do
>> it!
>>
>> Chele
>>
>> On 2/20/2007 9:56 AM, Richard Heckathorn wrote:
>>
>>> Greetings,
>>>
>>> I have a question that I just can't answer.
>>>
>>> Soda pop is of course a gas (CO2) dissolved in a liquid with the gas
>>> placed in the liquid under pressure. If the pop is warmed CO2 escapes.
>>> Thus less 'bite' to the taste. Shaking the pop causes
>>> CO2 to escape.
>>> When I pour the pop over ice, if fizzes greatly as
>>> CO2 escapes. In fact, so much so that the soda pop is left with little
>>>
>>> <>CO2 in it and tastes flat.
>>>
>>> What causes the rapid fizzing? (CO2 escape) as the soda pop is poured
>>> over ice. This is true even for soda pop being cooled in the
>>> refrigerator.
>>>
>>> Is there a website that discusses this? So far, I have found none.
>>>
>>> Thanks for help.
>>>
>>> Dick
>>
> v. much cut
>

***********************************************************************
Dr. Richard E. Berg, Professor of the Practice
Director, Physics Lecture-Demonstration Facility
U.S. mail address:
Department of Physics
University of Maryland
College Park, MD 20742-4111
Phone: (301) 405-5994
FAX: (301) 314-9525
e-mail reberg@umd.edu
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