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Posted: 9/9/2010 5:00:50 AM EDT
[Last Edit: 9/9/2010 2:11:13 PM EDT by captainpooby]
If you take an un-opened beer and shake it, does the pressure inside increase?


THE PRESSURE DOES NOT INCREASE:

  1. How bubbles form when you shake the bottle. You might think the pressure inside the bottle increases when shaken, but it does not.

"By shaking the bottle (capped), I could not increase the pressure above the pressure at which the soda was carbonated (about two atmospheres)," Bohren emails.

Something else causes the eruption of foam. What? Find out by a simple experiment. Stir a glass of soda with a spoon, and create a small whirlpool. Look! There's a string of bubbles in the vortex. That's the mechanism. The pressure of a simple vortex decreases toward the center. Bubbles form in the lower pressure.

  1. Why soda explodes out. Back to our capped bottle. Shake it. The shaking creates little whirlpools in the bottle. The pressure towards the center of the soda whirlpools is smaller than the surrounding soda pressure, so bubbles can develop and, when the pressure drops upon uncapping, bubbles will preferentially form in the whirlpool eddies.
    The surface tension, however, of a developing small bubble threatens to collapse the bubble before it can begin, unless the pressure inside the liquid surrounding the bubble is much lower than the pressure inside the bubble. And the capped bottle is still at essentially two atmospheres of pressure all over.

    But there is still a way for a bubble to start — as a microscopic bubble in the pits and cracks of tiny particles that float in the soda. A bubble simply begins as a crack. The 'crack' bubble already has surface areas that separate the bubble gas from the liquid soda. The surface-area work is done. Lots of minuscule bubbles develop in this way.

    Take the cap off, and the bottle pressure drops to one atmosphere. The bottle still contains whirlpools from the shaking. The pressure inside the whirlpool microscopic bubbles is roughly twice the surrounding liquid's pressure (because the bottler pumped the carbon dioxide gas into the soda at two atmospheres of pressure). The tiny bubbles, therefore, explode in size.

    The potential two-bottle volume of carbon dioxide gas that was dissolved in the liquid under two atmospheres of bottling pressure is now at only half bottling pressure. The two-bottle gas volume abruptly comes out of solution.

Soda spews!

Note that swirling whirlpool eddies are essential for getting soda to spew. "If you shake the soda violently, then let it sit for a while, removing the cap does not result in an explosion of foam," says Bohren.




Link Posted: 9/9/2010 5:08:31 AM EDT
Yes. CO2 comes out of solution and occupies the head space in the container.
Link Posted: 9/9/2010 5:09:12 AM EDT
Yes, but the treadmill has to be set at a 2% incline.
Link Posted: 9/9/2010 5:21:48 AM EDT
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?
Link Posted: 9/9/2010 5:23:26 AM EDT

Originally Posted By captainpooby:
If you take an un-opened beer and shake it, does the pressure inside increase?

Yes. When the CO2 is diffused in the water, the intermolecular forces (mostly hydrogen bonding since beer is almost all water) prevents the gas from behaving like a gas and exerting pressure on its environment. Shaking causes it to concentrate into bubbles which frees it from the solution so the pressure inside the bottle increases. As to why bubbles start from just shaking I forget.....Chem 2 was a long time ago.
Link Posted: 9/9/2010 5:24:32 AM EDT
Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?


Gas expands when it comes out of solution. Expansion in a fixed volume container = increased pressure. Shaking it encourages this process, which is why soda, beer, etc explodes when you do it.

Kind of like how water expands when it freezes (but has a lower freezing point when salts are dissolved within it): molecules do funny things depending on the tempurature, pressure and solution.
Link Posted: 9/9/2010 5:24:37 AM EDT

Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?

The container expands.

Link Posted: 9/9/2010 5:25:55 AM EDT
Take an open 2 liter bottle of soda and shake it. It will go from "soft" to "hard" the same thing happens in a glass bottle.
Link Posted: 9/9/2010 5:26:02 AM EDT
Originally Posted By Waveform:

Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?

The container expands.



So, my glass bottle will expand if shaken?

Link Posted: 9/9/2010 5:26:53 AM EDT
Originally Posted By Waveform:

Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?

The container expands.



I realize that. The statement made it sound like something else occupied that space. It's not getting displaced it's expanding.
Link Posted: 9/9/2010 5:27:15 AM EDT

Originally Posted By mcnizzle:


So, my glass bottle will expand if shaken?


Yes.
Link Posted: 9/9/2010 5:29:44 AM EDT
Originally Posted By jmarkma:
Then what occupies the space when it hasn't been shaken?


CO2, of course. But when the can is cold and undisturbed, most of the CO2 dissolves into the beer.

Simple test: go buy a 2L soda from the store and put it in your fridge, get it nice and cold. Take it out carefully and give it a squeeze. Now take it outside and give it a good whack against something hard (don't break it, you fool) or shake the shit out of it. Now try squeezing the bottle again: it should be much more difficult to compress.

Incidentally, this is why soda bottles make good pressure vessels for all sorts of fun home-science experiments: they have to withstand a LOT of pressure during the carbonation process and shipping.
Link Posted: 9/9/2010 5:32:35 AM EDT
[Last Edit: 9/9/2010 5:34:44 AM EDT by HoodyHoo21]
Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?


CO2, but at a lower pressure. Most of the CO2 is dissolved in the water.

Carbonated beverages are super saturated with respect to CO2. Meaning they force the water in the beverage to absorb more CO2 then it would like because they do it under pressure. This is why it bubbles off when you open the bottle and let it sit in the open air.
Link Posted: 9/9/2010 5:51:39 AM EDT
[Last Edit: 9/9/2010 5:53:17 AM EDT by Schadenfreuda]

Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?

Less pressure.

Originally Posted By mcnizzle:

So, my glass bottle will expand if shaken?


Yes, but not enough to notice.

Glass is actually a plastic.
Link Posted: 9/9/2010 5:56:56 AM EDT
I will post the answer later. It's locked in a box and I can't find the key.
Link Posted: 9/9/2010 6:38:38 AM EDT
Yes, but It's a sealed container, so its mass and weight stay the same. Unless you take it from Denver to Baltimore, then the weight will be slightly more, but mass stays the same.

Put a mothball in it, then shake it.
Link Posted: 9/9/2010 6:38:45 AM EDT
Don't forget that shaking also adds energy.
Link Posted: 9/9/2010 7:30:43 AM EDT

Originally Posted By gogoquadzilla:

Put a mothball in it, then shake it.

Some friend you are, trying to ruin this guy's brew!
Link Posted: 9/9/2010 7:35:22 AM EDT
Actually, yes. Glass is a liquid. The expansion is probably not noticeable - probably not measurable in a practical sense.

As to glass being a liquid, if you look at a really old window, you will find the bottom of the glass is thicker than the top, because the glass has been flowing....
Originally Posted By mcnizzle:
Originally Posted By Waveform:

Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?

The container expands.



So, my glass bottle will expand if shaken?



Link Posted: 9/9/2010 7:42:54 AM EDT

Originally Posted By dorobuta:
Actually, yes. Glass is a liquid. The expansion is probably not noticeable - probably not measurable in a practical sense.



Read this and tell me what you think:

http://math.ucr.edu/home/baez/physics/General/Glass/glass.html
Link Posted: 9/9/2010 7:46:38 AM EDT

Originally Posted By Waveform:

Originally Posted By dorobuta:
Actually, yes. Glass is a liquid. The expansion is probably not noticeable - probably not measurable in a practical sense.



Read this and tell me what you think:

http://math.ucr.edu/home/baez/physics/General/Glass/glass.html

Oh that was very fulfilling to read as a nerd.... I feel naughty now.


Link Posted: 9/9/2010 7:50:43 AM EDT
Gas volume stays the same as more gas molecules (released from the liquid) occupy the non-liquid space. Thus, pressure increases. The amount of expansion in the aluminum / glass / kryptonite container is inconsequential.
Link Posted: 9/9/2010 8:02:42 AM EDT
Originally Posted By HoodyHoo21:
Originally Posted By jmarkma:
Originally Posted By Zoomer302:
Yes. CO2 comes out of solution and occupies the head space in the container.


Then what occupies the space when it hasn't been shaken?


CO2, but at a lower pressure. Most of the CO2 is dissolved in the water.

Carbonated beverages are super saturated with respect to CO2. Meaning they force the water in the beverage to absorb more CO2 then it would like because they do it under pressure. This is why it bubbles off when you open the bottle and let it sit in the open air.


It only becomes supersaturated once you open it.

Saturation curves are scaled with respect to temperature and pressure. CO2 gas goes into solution in water at a rate proportional to the partial pressure of CO2 and inversely proportional to the temperature of the water.

In the beer industry, carbonation levels are measured in "volumes" of CO2. One volume is equivalent to one liter of gas at STP dissolved into one liter of beer. Atmospheric partial pressure can sustain just above 1 volume. So true cask beer, which some think of as uncarbonated, is actually just slightly carbonated. In order to fully degas any fermented beverage, you must boil it (used for testing purposes), run it through a pressure drop (filtration in the case of wine, for example), agitation or some other method.

Budweiser/Miller/Coors are very heavily carbonated, generally between 2.75 and 3 volumes. Most craft beer is 2.25-2.5 volumes or so. Belgians are generally higher that all of them - 3-3.5 volumes - as they are bottle-conditioned to a high degree. The American style brown 12oz. glass bottle is only rated to 3 volumes or around 12-14psig at room temperature. Belgians come in 11.2 ounce bottles because they have thicker walls. In order to fit in the same size 6/4-pack carriers and on shelves, the glass is thicker while the OD is the same - so, less volume.

Shaking a beer degasses it via agitation. This increases the partial pressure of CO2 inside the headspace until a new equilibrium point is reached. If allowed to sit and rest for a while, the gas will go back into solution until the original equilibrium point is restored.
Link Posted: 9/9/2010 11:18:54 AM EDT
That's it? Come on people!
Link Posted: 9/9/2010 2:10:22 PM EDT
Bump for the answer.
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