Does tapping Coke can keep fizz from exploding?
Edward F. Zotti
It is commonly believed that if a can of soda pop you are about to
drink is shaken up first, you can keep the fizz from exploding out
when it's opened by first tapping around the rim of the can. I have
been asked to venture an opinion on the usefulness of this procedure.
I am inclined to think it's a crock but would rather have scientific
backing before saying so in public.
My understanding is that carbonation is produced by forcing CO2 into
solution with H20 under pressure. Shake up the can and some of the CO2
comes out of solution and squeezes into the air space at the top of
the can. Wait a while and vapor pressure will eventually force the
liberated CO2 back into solution and eventually all will be as before?
OK so far? Now, I can't see any possible way that tapping on the can
would force CO2 back into solution any quicker. (Experiments in the
back yard tend to confirm this.) Am I missing anything or is this in
fact just the myth it appears to be?
One more thing. Warm pop that has been shaken up and then opened
fizzes a lot more than cold pop. Is this purely a consequence of
Charles' law? If so, would chilling be a good way to forestall a
geyser next time you drop a warm can of Jolt?
Replies by e-mail appreciated. For a newspaper column. -Ed
Mitch Rowe
In <4odvc8$k...@news.acns.nwu.edu> "Edward F. Zotti"
Well, ever pour pop into a glass? See how alot of the bubbles stick to
the side. As I understand it, this happens inside a can of pop too.
When you open it it QUICKLY rushes to the top so fast it brings pop
with it. By tapping the can you knock loose the bubbles from the sides.
Now, weather this acutully orks or not is a differnt story. I think if
a can is really shaken this does no good, but for just rough handling(
i.e. someone tossing it to you) I think it helps. Remember this is just
my oppinion so don't quote me.
M. Rowe
g...@chem.duke.edu
big...@ix.netcom.com(Mitch Rowe) wrote:
>In <4odvc8$k...@news.acns.nwu.edu> "Edward F. Zotti"
><ezo...@merle.acns.nwu.edu> writes:
>
>>
>>OK so far? Now, I can't see any possible way that tapping on the can
>>would force CO2 back into solution any quicker. (Experiments in the
>>back yard tend to confirm this.) Am I missing anything or is this in
>>fact just the myth it appears to be?
>>
>>Replies by e-mail appreciated. For a newspaper column. -Ed
>
>Well, ever pour pop into a glass? See how alot of the bubbles stick to
>the side. As I understand it, this happens inside a can of pop too.
>When you open it it QUICKLY rushes to the top so fast it brings pop
>with it. By tapping the can you knock loose the bubbles from the sides.
>Now, weather this acutully orks or not is a differnt story. I think if
>a can is really shaken this does no good, but for just rough handling(
>i.e. someone tossing it to you) I think it helps. Remember this is just
>my oppinion so don't quote me.
>
> M. Rowe
I think that your theory is how that story originated. However,
the physics theory that I know says that most of the bubbles form
after the can is opened because of the sudden lowering of pressure.
Tapping can't roosen bubbles that haven't formed yet. So I doubt
that the technique works. Just a typical superstition.
Of course, if there are large amounts of bubbles present before the
can is opened, then the technique may work. Maybe small amounts of
warming creates bubbles in the can (releasing gas by Henry's Law) and
then it works. I don't believe it myself, but maybe you could try
that in your backyard.
I think this would be an excellant science fair experiment for both
elementary and junior high school. Any takers?
David Rosen
dro...@inxs.chem.duke.edu
jason...@gecm.com
We have a man who is willing to shake a can for 10 seconds, and then tap
for 30 seconds, and then open the can in his face, as he is that
confident that it works. I will post the results of this experiment when
available.
Edward F. Zotti
scientific thoroughness, perhaps you could post the temperature of
the can. My experience has been that you can shake up a cold can of
pop quite a bit without necessarily getting an explosion when you
pop the lid--which may be why this myth persists. The real acid test
would be shaking up a warm can. -Ed
Justin D. Bukowski
Reply posted and mailed.
In article <4odvc8$k...@news.acns.nwu.edu>,
Edward F. Zotti <ezo...@merle.acns.nwu.edu> wrote:
>It is commonly believed that if a can of soda pop you are about to
>drink is shaken up first, you can keep the fizz from exploding out
>when it's opened by first tapping around the rim of the can. I have
>been asked to venture an opinion on the usefulness of this procedure.
>I am inclined to think it's a crock but would rather have scientific
>backing before saying so in public.
Or tapping the center of the top.
>My understanding is that carbonation is produced by forcing CO2 into
>solution with H20 under pressure.
Correct.
> Shake up the can and some of the CO2
>comes out of solution and squeezes into the air space at the top of
>the can. Wait a while and vapor pressure will eventually force the
>liberated CO2 back into solution and eventually all will be as before?
If the can has been at a constant temperature for some time, the
gas in solution and in the vapor space at top should be at equilibrium.
Shaking the can shouldn't change the distribution of CO2 or change the
pressure of the system. I believe a popular science magazine (the Amateur
Scientist column of _Scientific American_ ?) discussed this several years
ago, including attempts at determining the pressure in the can. The
author surmised that the act of shaking caused vortices in the beverage,
which served as nucleation sites for bubble formation when the pressure
was released by opening the can. Tapping the can took time, which allowed
the vortices to subside. Presumably, simply letting the can sit would
also work.
Another possibility is that shaking the can leaves bubbles attached
to the walls, which then serve as nucleation sites. Tapping the can
dislodges these bubbles, so they rejoin the vapor space at the top.
I would imagine that the presence or absence of such bubbles could be
determined via ultrasound imaging. Alas, my research fund won't permit
me to examine this further. The formation of such bubbles would probably
depend upon the surface tension of the beverage and the coating on the
inside of the can. Thus, it may be that tapping *is* important for
some beverages but not others.
>OK so far? Now, I can't see any possible way that tapping on the can
>would force CO2 back into solution any quicker. (Experiments in the
>back yard tend to confirm this.) Am I missing anything or is this in
>fact just the myth it appears to be?
Well, the proof is in the pudding. Shake two cans, tap one as the other
sits, then open both simultaneously. Since different beverages have
different surface tensions (different ability to support foaming), this
experiment would need to be carried out with a wide range of drinks.
>One more thing. Warm pop that has been shaken up and then opened
>fizzes a lot more than cold pop. Is this purely a consequence of
>Charles' law? If so, would chilling be a good way to forestall a
>geyser next time you drop a warm can of Jolt?
The solubility of gas in cold liquids is much higher than that in
hot liquids (note, when boiling water, that air comes out of solution
long before boiling starts.) Warm beverages will lose their carbonation
faster than cold. As for that Jolt, let it sit a minute, chilled or not.
>Replies by e-mail appreciated. For a newspaper column. -Ed
My pleasure, Cece.
Justin
Trinlay Khadro
Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
: It is commonly believed that if a can of soda pop you are about to
: drink is shaken up first, you can keep the fizz from exploding out
: when it's opened by first tapping around the rim of the can. I have
: been asked to venture an opinion on the usefulness of this procedure.
: I am inclined to think it's a crock but would rather have scientific
: backing before saying so in public.
IMHO and not at all scientific, is that Tapping the can makes the person
feel like they are doing SOMETHING while they wait.
the "fizz explosion" will settle down if one waits before opening
the container and opens it carefully.
(tapping also keeps their hands on the can that needs to be
opened carefully so they don't forget.)
I suppose it's experiment time, but I have only one can of soda
right now...
: the can. Wait a while and vapor pressure will eventually force the
: liberated CO2 back into solution and eventually all will be as before?
Yep, let it sit and it will "fix itself"
though it still helps to open the can or bottle slowly.
: Charles' law? If so, would chilling be a good way to forestall a
: geyser next time you drop a warm can of Jolt?
remember heat is a (dang forgot the word..I hate that!) well thing that
makes things happen faster because the molecules are "more excited"
when heated. So <Yah! Catalyst! that's the word!> Cool or cold sodas
would probably be less "explosive" (and they hold the fiz longer
warm sodas go flat much more quickly.)
tonywilk
<g...@chem.duke.edu> wrote:
>the physics theory that I know says that most of the bubbles form
>after the can is opened because of the sudden lowering of pressure.
>Tapping can't roosen bubbles that haven't formed yet. So I doubt
>that the technique works. Just a typical superstition.
> Of course, if there are large amounts of bubbles present before the
>can is opened, then the technique may work. Maybe small amounts of
>warming creates bubbles in the can (releasing gas by Henry's Law) and
>then it works. I don't believe it myself, but maybe you could try
>that in your backyard.
I believe that shaking a can of coke increases the internal pressure
but there is then less CO2 in solution, so why does it froth up when
opened ?
I think it's because of (high pressure) bubbles created during shaking
are still in the coke, so they expand when the pressure is released and
cause further frothing.
If there are no bubbles at all in the liquid, then I would guess that
higher or lower pressure (with fixed CO2 quantity) before the can is
opened would be irrelevant.
Wether tapping makes any difference - haven't a clue!
However... once opened, pouring quickly (avoid 'glugging' from the can)
into a glass makes the drink froth up a lot, but if you pour just a little
bit out then swirl it around to 'coat' the glass, then the rest will not
froth up so much - fewer nucleation points for the bubbles to form on
the glass.
Yours,
Tony Wilk
Eric Lucas
Edward F. Zotti wrote:
> I can't see any possible way that tapping on the can
> would force CO2 back into solution any quicker. (Experiments in the
> back yard tend to confirm this.) Am I missing anything or is this in
> fact just the myth it appears to be?
I've done some semi-controlled experiments in the past, and there does
seem to be a small difference. However, these are very subjective
experiments, and the effect seems to be pretty small, if it's actually
real.
*If there really is such an effect*, I might postulate that the sound
waves might help the CO2 redissolve faster--ultrasonic agitation is a
common, highly effective way to activate biphasic (usually solid-liquid)
processes. Compression/cavitation due to ultrasound waves in water can
lead to extremely high temperatures and pressures (I've heard 200 C and
10,000 psi) that are *highly* localized, even though the average
temperature and pressure are very close to ambient. I'm not suggesting
that anything approaching this in degree happens with single-agitation
low-energy sound waves like you get from tapping, but I suppose it might
be some similar effect.
> One more thing. Warm pop that has been shaken up and then opened
> fizzes a lot more than cold pop. Is this purely a consequence of
> Charles' law? If so, would chilling be a good way to forestall a
> geyser next time you drop a warm can of Jolt?
Yes, I believe so, to both questions. Be aware, however, that the rate
of dissolution will be slowed by chilling--as with any chemical process
with an activation energy, it'll happen faster at higher temperature.
(Warm cans of Jolt--that image harkens me back to my college days and
all-nighters! Yeesh!)
Time is of course the best way to keep a shaken can of pop from spraying
everywhere.
Eric
Stuart Beaton
>It is commonly believed that if a can of soda pop you are about to
>drink is shaken up first, you can keep the fizz from exploding out
>when it's opened by first tapping around the rim of the can. I have
>been asked to venture an opinion on the usefulness of this procedure.
>I am inclined to think it's a crock but would rather have scientific
>backing before saying so in public.
>
>My understanding is that carbonation is produced by forcing CO2 into
>solution with H20 under pressure. Shake up the can and some of the CO2
>comes out of solution and squeezes into the air space at the top of
>the can. Wait a while and vapor pressure will eventually force the
>liberated CO2 back into solution and eventually all will be as before?
>
>OK so far? Now, I can't see any possible way that tapping on the can
>would force CO2 back into solution any quicker. (Experiments in the
>back yard tend to confirm this.) Am I missing anything or is this in
>fact just the myth it appears to be?
>
One of Richard Feynman's books (I think it was) mentioned a demonstration
that showed that the pressure in a can did _not_ increase upon shaking -
and in fact there is no reason the CO2 should come out of solution. What
apparently _does_ happen is that when shaken, small bubbles from the
headspace get distrubuted throughout the interior of the can. Then when
it is opened, these bubbles expand rapidly, forcing out soda. Tapping the
can dislodges these bubbles, which rise back to the headspace, where they
do no harm when the pressure is released.
>One more thing. Warm pop that has been shaken up and then opened
>fizzes a lot more than cold pop. Is this purely a consequence of
>Charles' law? If so, would chilling be a good way to forestall a
>geyser next time you drop a warm can of Jolt?
>
>Replies by e-mail appreciated. For a newspaper column. -Ed
Gases dissolve better in cold liquids, so chilling decreases the pressure
and slows loss of carbonation.
Now make sure you have the correct answer (which I hope I provided!)
before you print it!
Happy editing,
Stuart Beaton
sbe...@du.edu
Triple Quadrophenic
In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
(Stuart Beaton) says...
>
>
>One of Richard Feynman's books (I think it was) mentioned a demonstration
>that showed that the pressure in a can did _not_ increase upon shaking -
>and in fact there is no reason the CO2 should come out of solution.
I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
preferably one that's had some removed. Open it up so that it's at
atmospheric pressure then put the lid on. If you squeeze the bottle now it
offers little resistance. Now shake the bottle and try squeezing again - the
bottle will be much firmer.
I've encountered cans that I've been able to push in slightly before opening
them. After a good shake they're as incompressible as ordinary cans.
--
-- BEGIN NVGP SIGNATURE Version 0.000001
Frank J Hollis, Mass Spectroscopy, SmithKline Beecham, Welwyn, UK
Frank_H...@sbphrd.com or fj...@tutor.open.ac.uk
All Opinions My Own (So My Employer Tells Me)
DALE OLIVE
As a science teacher I've done this as a demo many times and get about a
90-95% success rate! I think the reason why I do get failures is because
I haven't tapped the top hard enough! It doesn't matter how hard you
shake it as I usually ask a student to do the shaking for me and they live
for my failures . . .fortunately, for me, I usually dissappoint them!
try it . . .I usually use a ruler to tap the sides and top . . .and keep a
towel handy for those 5-10%.
Another good demo with soda is to get one of those "ultra sonic"cleaners
that clean things in a soap bath that is vibrating many times a second.
take a two liter bottle of soda, put a small hole in the top of the lid
and set it in the cleaner. You can get a geyser that shotts 20-30 feet
into the air.
One of my favorite pressure demos is the "Alka-rocket" which I invented a
few years ago. Take a "clear - fuji" film cannister and make a rocket
out of it by taping an index card to the annister and affixing a index
card nose cone on that. Put a teasppon of water in the cannister and one
alka-seltzer tablet. Put the lid on quickly and place lid side down on
the ground. In about 15 seconds enough pressure builds p to shoot the
rocket 15-20 feet or more into the air. Try it , it works!
Philip Gibbs
Triple Quadrophenic wrote:
>
> In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
> (Stuart Beaton) says...
> >
> >
> >One of Richard Feynman's books (I think it was) mentioned a demonstration
> >that showed that the pressure in a can did _not_ increase upon shaking -
> >and in fact there is no reason the CO2 should come out of solution.
>
> I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
> preferably one that's had some removed. Open it up so that it's at
> atmospheric pressure then put the lid on. If you squeeze the bottle now it
> offers little resistance. Now shake the bottle and try squeezing again - the
> bottle will be much firmer.
>
> I've encountered cans that I've been able to push in slightly before opening
> them. After a good shake they're as incompressible as ordinary cans.
>
This question comes up in sci.physics from time to time so I
suppose it will have to go into the Physics FAQ (or should
that be fizz'iks FAQ, groan).
There are two questions under discussion:
1) Does tapping the can after it has been shaken stop it from frothing
when opened?
The answer is yes. After being shaken the can has bubbles on the side.
These will act as nucleation sites and expand upon opening and this is
what causes the frothing. If you tap the can the bubbles are dislodged
and float to the surface where they burst. The gas is not redissolved,
it is just displaced back to the top. If you don't believe it try it. Do
it with two cans, shake both at the same time, tap or roll one, then
open them both. To be really scientific do the experiment double blind
with several cans.
2) Does the pressure in a coke/beer can increase when shaken?
If the can is already in equilibrium then the pressure will not
increase by any easily perceptable amount. Again, if you don't
beleive it, try an experiment double blind with several cans.
If the can is not in equilibrium then shaking the can will bring
it rapidly to equilibrium and a noticeable pressure change is
possible. This is the case for a bottle which has just been opened
and then resealed. It is then no longer in equilibrium. It could
also happen if the can has recently undergone a tempertaure change.
Take a room temperature can and throw it into a bucket of ice water
for a minute or so. take it out, now try shaking it and see if
the pressure changes (let me know what happens because I have
never tried this one)
====================================================
Phil Gibbs p...@pobox.com http://pobox.com/~pg
Edward F. Zotti
Philip Gibbs <philip...@pobox.com> wrote:
> There are two questions under discussion:
>
> 1) Does tapping the can after it has been shaken stop it from frothing
> when opened?
>
> The answer is yes. After being shaken the can has bubbles on the side.
> These will act as nucleation sites and expand upon opening and this is
> what causes the frothing. If you tap the can the bubbles are dislodged
> and float to the surface where they burst. The gas is not redissolved,
> it is just displaced back to the top. If you don't believe it try it. Do
> it with two cans, shake both at the same time, tap or roll one, then
> open them both. To be really scientific do the experiment double blind
> with several cans.
I am having a hard time buying this. First, it doesn't mesh with my own
experience, and second, it doesn't make sense in light of what I know
about what happens inside a soft drink container when you shake it up.
Jearl Walker in the Dec 1981 Amateur Scientist column in Scientific
American says that when you shake up a can of pop cavitation due to
turbulence leads to the formation of hundreds of thousands of tiny
bubbles throughout the liquid. When the can is opened, the CO2 takes
advantage of the increased surface area afforded by these bubbles to
come out of solution in abundance.
I suppose it's possible that some of these bubbles may adhere to the
sides of the can, but surely only a tiny fraction of the total. Even
if tapping were to dislodge all these bubbles, which is questionable
in itself, it seems unlikely this would reduce the fizziness
appreciably.
Having said that, I am now going to go out in the back yard with
a couple cans of room temperature pop (much more prone to explosive
fizziness than the cold stuff), shake them both up good, tap one with,
let's see, a piece of metal pipe, open both, and see what happens.
> 2) Does the pressure in a coke/beer can increase when shaken?
>
> If the can is already in equilibrium then the pressure will not
> increase by any easily perceptable amount. Again, if you don't
> beleive it, try an experiment double blind with several cans.
This I'll buy.
I'll report back on my experiments within the hour. Stand by. -Ed
Edward F. Zotti
> > 1) Does tapping the can after it has been shaken stop it from frothing
> > when opened?
> >
> > The answer is yes. After being shaken the can has bubbles on the side.
> > These will act as nucleation sites and expand upon opening and this is
> > what causes the frothing. If you tap the can the bubbles are dislodged
> > and float to the surface where they burst. The gas is not redissolved,
> > it is just displaced back to the top. If you don't believe it try it. Do
> > it with two cans, shake both at the same time, tap or roll one, then
> > open them both. To be really scientific do the experiment double blind
> > with several cans.
>
> I am having a hard time buying this.
[discussion of fizz theory deleted]
> Having said that, I am now going to go out in the back yard with
> a couple cans of room temperature pop (much more prone to explosive
> fizziness than the cold stuff), shake them both up good, tap one with,
> let's see, a piece of metal pipe, open both, and see what happens.
OK, I'm back. To all you proponents of the tapping school, sorry, I'm
just not seeing what you're seeing.
Here's what I did. I got two 12-oz. aluminum cans of Coca-Cola Classic
that had been sitting in the case at room temperature (currently 74
degrees F) for a week. I simultaneously shook both with a vigorous
longitudinal motion (in my less mature days I would have described
this as hand job style) 60 times. Then I set both cans on the concrete
pavement out back and immediately tapped one can 30 times around the
top rim with a 12" length of metal conduit. Then I popped the tops of
both cans simultaneously. There was no noticeable difference in
fizziness.
I repeated the process, this time tapping one can in the center of the
lid for good measure in addition to around the rim. Again, no noticeable
difference.
[brief interval]
Just got off the phone with Jearl Walker, physics prof at Cleveland
State, textbook author, and author for many years of the Amateur
Scientist column in Scientific American. As noted previously, Jearl
wrote about the fizz question in the Dec 1981 SA. He says he got a
lot of people writing him afterward claiming that tapping on the
can reduced the fizz. He does not think this accomplishes much and
attributes the persistence of this practice to the same suppressed
macho instinct that makes them tap the ends of their cigarettes
before lighting up.
If anybody can suggest a tapping procedure that will produce a
noticeable difference in fizziness, now is the time to come forward.
Thanks. -Ed
Philip Gibbs
Edward F. Zotti wrote:
>
> OK, I'm back. To all you proponents of the tapping school, sorry, I'm
> just not seeing what you're seeing.
>
DALE OLIVE wrote:
> As a science teacher I've done this as a demo many times and get about a
> 90-95% success rate! I think the reason why I do get failures is because
> I haven't tapped the top hard enough!
Seems we have one for and one against. I will try it myself
but I only have bottled beer in the fridge which might not be the
same as canned cola.
--
Barre K Bollinger
On 28 May 1996, Justin D. Bukowski wrote:
> Reply posted and mailed.
>
> In article <4odvc8$k...@news.acns.nwu.edu>,
> Edward F. Zotti <ezo...@merle.acns.nwu.edu> wrote:
> >It is commonly believed that if a can of soda pop you are about to
> >drink is shaken up first, you can keep the fizz from exploding out
> >when it's opened by first tapping around the rim of the can. I have
> >been asked to venture an opinion on the usefulness of this procedure.
> >I am inclined to think it's a crock but would rather have scientific
> >backing b> Or tapping the center of the top.
>
> >My understanding is that carbonation is produced by forcing CO2 into
> >solution with H20 under pressure.
>
> Correct.
>
I believe you guys are making this more complicated than is necessary.
When a can is shaken, KE is transferred to the cola. CO2 is boiled off
due to the increase, but some is kept in the soda because of the limited
volume. When one opens the can, this CO2 in the soda is rapidly released
(foam). I can see no reason that tapping the can will reduce
this KE of the CO2. On the contrary it would add to it. Tapping is
probably BS (although it is still a habit of mine that I cannot break from
high school beer drinking days.
B-> Barre Bollinger bkbo...@mail.uccs.edu
Robert Wiegand
"Edward F. Zotti" <ezo...@merle.acns.nwu.edu> writes:
>It is commonly believed that if a can of soda pop you are about to
>drink is shaken up first, you can keep the fizz from exploding out
>when it's opened by first tapping around the rim of the can. I have
>been asked to venture an opinion on the usefulness of this procedure.
>I am inclined to think it's a crock but would rather have scientific
>backing before saying so in public.
I don't really believe this either. I think that some people over estimate
the odds of having a can "explode". When it doesn't happen they think that
their tapping is working.
I've dropped cans onto the floor and then opened them with no problem.
They really aren't that sensitive.
--
----------------------------------------------------------------------------
Bob Wiegand | Education makes a people easy to lead, but
Motorola Inc. | difficult to drive; easy to govern, but
bwie...@sesd.cig.mot.com | impossible to enslave - Henery Peter Brougham
Barre K Bollinger
I think everyone is making this problem more complicated than is
necessary. Shaking a can of soda adds KE to the soda (including its CO2).
Some CO2 is boiled off due to this and some is kept in the liquid due to
limited volume (pressure problem) of the can. When you open the can, the
CO2 in the liquid is rapidly released (causing foam). Tapping on the can
does nothing except maybe add a bit more energy (making it worse).
B-) Barre Bollinger bkbo...@mail.uccs.edu
bbows@hr.house.gov (or) bruce@lee.house.gov
DALE OLIVE <da...@kalama.doe.hawaii.edu> wrote:
>As a science teacher I've done this as a demo many times and get about a
>90-95% success rate! I think the reason why I do get failures is because
>shake it as I usually ask a student to do the shaking for me and they live
>for my failures . . .fortunately, for me, I usually dissappoint them!
>try it . . .I usually use a ruler to tap the sides and top . . .and keep a
>towel handy for those 5-10%.
>Another good demo with soda is to get one of those "ultra sonic"cleaners
>that clean things in a soap bath that is vibrating many times a second.
>take a two liter bottle of soda, put a small hole in the top of the lid
>and set it in the cleaner. You can get a geyser that shotts 20-30 feet
>into the air.
>One of my favorite pressure demos is the "Alka-rocket" which I invented a
>few years ago. Take a "clear - fuji" film cannister and make a rocket
>out of it by taping an index card to the annister and affixing a index
>card nose cone on that. Put a teasppon of water in the cannister and one
>alka-seltzer tablet. Put the lid on quickly and place lid side down on
>the ground. In about 15 seconds enough pressure builds p to shoot the
>rocket 15-20 feet or more into the air. Try it , it works!
I remember when I was in high school, I used to work at
a grocery store. When Coke's delivery truck would come,
this guy at my job would throw up a can and then hit it
with a baseball bat. Then, the can would fly through the
air and hit the ground with an bang.
092775078900000079834798754759370949257019692700019848970333333797823098709257897350729843982384489349079239349397489437509488979379=
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4759370949257019692700019848970333333797823098709257897350729843982384489349079239349397489437509488979379345784832093434
Wayne Richardson
> I can see no reason that tapping the can will reduce
>this KE of the CO2. On the contrary it would add to it. Tapping is
>probably BS (although it is still a habit of mine that I cannot break from
>high school beer drinking days.
>
>B-> Barre Bollinger bkbo...@mail.uccs.edu
>
And some people say that there is nothing to be gained from beer drinking in
high school.
Cheers,
Wayne Richardson
Bruce Burke
I remember a friend doing that many years ago(guess I was in High School then).
His explaination was that it made the drink somehow sweeter.
Bruce Burke
Bryant Fujimoto
Frank_H...@sbphrd.com (Triple Quadrophenic) writes:
>In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
>(Stuart Beaton) says...
>>
>>
>>One of Richard Feynman's books (I think it was) mentioned a demonstration
>>that showed that the pressure in a can did _not_ increase upon shaking -
>>and in fact there is no reason the CO2 should come out of solution.
>I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
>preferably one that's had some removed. Open it up so that it's at
>atmospheric pressure then put the lid on. If you squeeze the bottle now it
>offers little resistance. Now shake the bottle and try squeezing again - the
>bottle will be much firmer.
In order for this to be a valid test, you have to open it up and let
it come to equilibrium at atmospheric pressure before closing. That
is you have to let the soft drink go flat. Then, if you close it and
shake you will not get a significant change in pressure inside. If
you don't wait, then when you close the top, the contents of the bottle
are not at equilibrium, and shaking speeds the release of dissolved
gases into the space above the liquid. After it reaches equilibrium,
the situtation should be the same as before you opened it the first
time, that is the pressure should not change if you shake the can or
bottle.
>I've encountered cans that I've been able to push in slightly before opening
>them. After a good shake they're as incompressible as ordinary cans.
Can you suggest a reason why shaking a can should cause CO2 to leave
solution? That is, why does shaking the can cause the contents of
the can to shift from an equilibrium to a nonequilibrium condition?
Bryant Fujimoto
fuji...@u.washington.edu
Martin Trump
In article <4oh3c1$8...@phunn1.sbphrd.com>, Triple Quadrophenic
<Frank_H...@sbphrd.com> writes
>In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
>(Stuart Beaton) says...
>>
>>
>>One of Richard Feynman's books (I think it was) mentioned a demonstration
>>that showed that the pressure in a can did _not_ increase upon shaking -
>>and in fact there is no reason the CO2 should come out of solution.
>
>I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
>preferably one that's had some removed. Open it up so that it's at
>atmospheric pressure then put the lid on. If you squeeze the bottle now it
>offers little resistance. Now shake the bottle and try squeezing again - the
>bottle will be much firmer.
Half a mo! Compare apples with apples. A can of whatever has probably
been sealed for a month or more. Do the same and try your experiment
again!
Regards
--
Martin Trump
Marcus H. Mendenhall
Actually, the tapping is not supposed to put the CO2 back in solution.
The idea is that it causes all the bubbles which are adhering to the
side of the can to let go and float to the top. Then, when you open the
can, the gas escapes without dragging all the soda with it. It actually
works very well.
Marcus Mendenhall
tonywilk
j...@condor.cchem.berkeley.edu (Justin D. Bukowski) wrote:
[bulk of post snipped]
>Well, the proof is in the pudding. Shake two cans, tap one as the other
>sits, then open both simultaneously. Since different beverages have
>different surface tensions (different ability to support foaming), this
>experiment would need to be carried out with a wide range of drinks.
Well would you believe it....
I just went into the kitchen, two identical cans of 'Lilt' at room temp
shook 'em both very vigorously for 30 secs, then for the next 30 secs
let one stand and tapped the other all over.
The I opened them both at the same time.
psfft. psfft.
Just when you want a can of pop to spew everywhere and it acts as flat
as water !
I'd try Coke, but I've only got a couple of 2L bottles...
Yours,
Tony Wilk
Paul Glaser
okay.. here we go.
1) why does shaking make Cola fizz?
well, as you shake the can you are setting up random compressional
waves in the fluid inside, due to the sloshing around in the cola (just
like sound). As compresssional waves have regions of high medium density
and low medium density, the wave will serve to allow CO2 to leave solution
from the low density regions.
Even though the cola (as most fluids) will be essentially
non-compressible, the waves will nonetheless allow the CO2 to leave
solution due to the compresssion/decompresssion. An extreme example of
this would be the ultrasound phenomenon mentioned in previous posts.
2) why toes tapping the top of a can stop some fizzing?
I've seen people tap gently on the top of a can, and I've never really
believed in that procedure. However, when i'm about to open a can, i will
often press quite firmly on the pop-top region of the can's top for a few
seconds. My rationale: the construction of the can incorporates an area
designed to mechanically fail (the pop-top) when pressed on hard enough
(by the tab), thus opening the can. When the top is actually popped,
there is essentially explosive decompression inside the can. Anything
that can be done to make the process more gradual, or impart less of a
rapid change in the system, should allow the whole system to come to
equilibrium in a kinder, gentler manner. By pressing on the pop-top, I am
presumably weakening the seal to effect a less violent can-opening
process.
My explanation might be a bit contorted, but I'll swear by the results
(beer, soda, fruit drinks, etc..)
later.
PG
Bryant Fujimoto
>okay.. here we go.
>1) why does shaking make Cola fizz?
> well, as you shake the can you are setting up random compressional
>waves in the fluid inside, due to the sloshing around in the cola (just
>like sound). As compresssional waves have regions of high medium density
>and low medium density, the wave will serve to allow CO2 to leave solution
>from the low density regions.
>Even though the cola (as most fluids) will be essentially
>non-compressible, the waves will nonetheless allow the CO2 to leave
>solution due to the compresssion/decompresssion. An extreme example of
>this would be the ultrasound phenomenon mentioned in previous posts.
I don't understand this. Something doesn't sound quite right to me
and some questions/comments spring to mind.
1. Since the can is at equilibrium before you start to shake it, why
should any of the CO2 want to leave the solution? (Or to be more
pedantic, why should Delta A for the transfer of CO2 from dissolved
in the soda to the gas phase be negative?)
2. Does the solubility of CO2 in water depend signficantly on the
density? I would be surprised if you could get more than a minute
change in soft drink density by shaking the can, so you would need
a very substantial density dependence to cause a noticable change
in the solubility. Finally, if there is a net flow of CO2 from the
minutely lower density regions caused by shaking into the gas phase,
would there be a net flow of CO2 from the gas phase into the minute
higher density regions?
3. After you stop shaking, if you do have a higher pressure in the
space above the soft drink, why should that cause the can to foam
over when opened?
4. The ultrasound phenomena sounds like something that will provide
nucleation sites for the dissolved gas to leave solution. I'm not
sure it demonstrates that the pressure is rising due to the release
of CO2 when the can/bottle is sealed.
5. Does anyone see anything wrong with my simplistic thermodynamic
thinking? There may be some effect related to turbulent fluid flow
(cavitation?) about which I know nothing which might have some
bearing on this discussion.
Bryant Fujimoto
fuji...@u.washington.edu
Philip Gibbs
In fact it would not be the density which counts it would be the
pressure. Pressure changes effect solubility of gases and there
will be pressure changes in the liquid even though there will be
only very tiny changes in density.
In theory pressure changes can induce gas to come out of solution.
When the pressure reduces suddenly gas bubbles will form. Pressure
increase might not be so effective in putting the gas back into
solution since it can only act where there is a gas liquid boundary.
So *in theory* shaking or applying ultrasound might lead to an
increase of pressure even in a can which was previously in
equilibrium.
In the course of a previous thread on this subject a couple of
years ago I too thought of this idea. There were sceptics so I
decided to test it experimentally. I took six cans of beer
which were in equilibrium. I marked three of them on the botton
and shook those three as hard as I could. I then got someone
to shuffle the cans so I no longer knew which has been shaken.
By feeling the pressure in each can I tried to guess which
were the shaken ones by using the theory that they should
have a higher pressure. I could not detect much difference
but I picked out the three which I guessed had the
highest pressure anyway.
Then the moment of truth. I looked on
the bottom of the cans to see if I had correctly picked those
which had been shaken. To my great dismay I found that I had
picked the other three! In other words, if this proves
anything, it is that there is a decrease in pressure on
shaking. More likely there is no perceptible pressure change
and my choice was a fluke.
I encourage others to try this simple experiment and report back
the results. It will be interesting to see if there is any
effect with other fizzy drinks.
Cheers!
Philip Gibbs
Philip Gibbs wrote:
> anything, it is that there is a decrease in pressure on
> shaking. More likely there is no perceptible pressure change
> and my choice was a fluke.
>
I should add that this does not mean that shaking does not
cause bubbles to form. If you shake a transparent bottle
it is easy to see that bubbles do form and this is
why it froths when opened after shaking.
TERENCE LEE VAN ZYL
In article <31AC6E...@pobox.com> Philip Gibbs <philip...@pobox.com> writes:
>From: Philip Gibbs <philip...@pobox.com>
>Subject: Re: Does tapping Coke can keep fizz from exploding?
>Date: Wed, 29 May 1996 17:36:17 +0200
>Edward F. Zotti wrote:
>>
>> OK, I'm back. To all you proponents of the tapping school, sorry, I'm
>> just not seeing what you're seeing.
>>
>DALE OLIVE wrote:
>> As a science teacher I've done this as a demo many times and get about a
>> 90-95% success rate! I think the reason why I do get failures is because
>> I haven't tapped the top hard enough!
>Seems we have one for and one against. I will try it myself
>but I only have bottled beer in the fridge which might not be the
>same as canned cola.
The tapping on the top of the can creates ripples in the liquid in the can.
These ripple increase the area of the surface. The dissolution of CO2 back
into the can is mass transfer llimiting. If the area is increased, the mass
transfer of CO2 will increase, resulting in faster absorbtion of the gas
into the liquid.
Philip Gibbs
Quite possibly,
Anyway, during my lunch hour I did an experiment with two cans
of chilled classic coke. I shook both vigorously. Then I tapped
one all around its side with a spoon for about a minute while the
other stood undisturbed.
When I opened them neither frothed significantly but I did notice
more bubbles coming to the surface in the untapped can. Since I
did not do the experiment blind I think the result is pretty
inconclusive.
However, it certainly seems that bubbles dissipate in cola pretty
quickly whether they are tapped or not. If the cans are left for
just a short while after shaking they will not froth much in any
case.
The experiment needs to be repeated with beer for which the bubbles
may remain longer. A control can in the experiment is essential.
By the way, you can hear the bubbles by holding the can to your ear.
K. Murray
>drink is shaken up first, you can keep the fizz from exploding out
>when it's opened by first tapping around the rim of the can.
I couldn't find this in a quick pass of the AFU FAQ. If it isn't
there, it should be.
K. Murray
William R. Penrose
In article <4oi9eg$k...@neon.house.gov> "bb...@hr.house.gov (or) br...@lee.house.gov" <bb...@hr.house.gov> writes:
>I remember when I was in high school, I used to work at
>a grocery store. When Coke's delivery truck would come,
>this guy at my job would throw up a can and then hit it
>with a baseball bat. Then, the can would fly through the
>air and hit the ground with an bang.
I once saw a case of pop cans fly off a truck and scatter on the ground. As
the other traffic hit the cans, it made a sound like a small war.
************************************************************
Bill Penrose, Sr. Scientist, Transducer Research, Inc.
600 North Commons Drive, Suite 117
Aurora, IL 60504
708-978-8802, fax -8854, email wpen...@interaccess.com
************************************************************
Purveyors of fine gas sensors and
contract R&D to this and nearby galaxies.
************************************************************
Bo Bradham
The statement attributed to Zotti is true. Whether is is true
that tapping the can actually prevents the gaseuous eruption of its
contents, I don't know, but I'll bet you can find the last several
afu threads on this topic on dejanews. People have posted much
anecdotal and pseudo-experimental evidence, along with ample
theorizing to support their conclusions. You'll have to sort
thru it for yourself.
Bo "I couldn't find it in the Faq either." Bradham
--
"We consider that any man who can fiddle all through one of
those Virginia Reels without losing his grip, may be depended
upon in any kind of musical emergency."
-- Mark Twain.
STUART P. BEATON
Triple Quadrophenic (Frank_H...@sbphrd.com) wrote:
: In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
: >
: >
: >One of Richard Feynman's books (I think it was) mentioned a demonstration
: >that showed that the pressure in a can did _not_ increase upon shaking -
: >and in fact there is no reason the CO2 should come out of solution.
: I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
: preferably one that's had some removed. Open it up so that it's at
: atmospheric pressure then put the lid on. If you squeeze the bottle now it
: offers little resistance. Now shake the bottle and try squeezing again - the
: bottle will be much firmer.
Let me clarify - I assumed an unopened can at thermal equilibrium. If you
open it, you destroy the equilibrium between the gas above the soda and the
gas dissolved in it - that's why you see bubbles rising in an open
container but not in a sealed one >which has had time to build up the
pressure again and return to equilibrium<. I can certainly believe that
shaking a de-pressurised bottle would encourage equilibrium by producing
more nucleation sites.
: I've encountered cans that I've been able to push in slightly before opening
: them. After a good shake they're as incompressible as ordinary cans.
Can't say I've ever encountered that. I assume the cans were not changing
temperature? For instance, upon removing one from the refridgerator the
gas in the headspace will warm up quickly, as well as the top of the can.
Shaking at this time will put a bunch of liquid in contact with the warm
gas and metal, increasing its temp, and increasing the pressure.
(And let us not ignore physiological factors - a vigorous shake will
fatigue one's hand, making the can >feel< harder :) )
On an unrelated (?) note, I find interesting that some cans you've
encountered apparently lack pressure, compared to 'ordinary' cans. Is this
faulty manufacturing, insufficient filling, pinhole leakage? I don't think
I've ever heard of this before (not that I make it a habit to ask!)
Stuart Beaton
sbe...@du.edu
: --
Joel Golden
> Stuart Beaton
> sbe...@du.edu
Perchance the gas is allowed to take up more volume in its free state as
opposed to when its bound up in the liquid.
An interesting thing I've noticed: When opening a bottle of club soda, open
the cap just slightly so that the gas can barely escape. If you watch the
bubbles forming you may notice that every 2 or so seconds they will wax and
wane. I think that, due to the escaping gas, the CO2 equilibrium between gas
and fluid comes and goes. Any other explanations?
Joel Golden
Martin Heinz
Hopefully thinking before posting before thinking, Bo Bradham wrote:
[...someone asked if tapping soda cans prevents foaming...]
[...]
: afu threads on this topic on dejanews. People have posted much
: anecdotal and pseudo-experimental evidence, along with ample
I did try some "pseudo-experiments" (thank you very much) which led me to
believe that tapping does *not* effect any difference.
However, the variations of "tapping a soda can" are sheer endless.
People argued:
1) It depends on *how* you tap (Top? Side? Flicking a finger? Knocking?)
2) Just *when* is a soda can agitated enough for the hypothesized effect
to work? (Shaking? Dropping? How much? How high? Does it count if is
scooped up by a plane and dropped in a forest fire?)
3) It depends on what *kind* of soda you take -- I used Diet Coke, then
someone said "noooo, the NutraSweet makes everything obsolete"
4) It depends on the temperature of the soda.
5) It depends on the country the experiment is conducted in, because
"tapping" is one of the many words in Inuit related to soda and
means "sticking a can up your butt"
You be the judge.
I'd give it a Fb.
Martin "oh, should you happen to die, you could have this maybe answered
by the Make-A-Wish Foundation" Heinz
--
Martin Heinz * he...@math.utexas.edu *http://www.ma.utexas.edu/users/heinz
"In 1992, handguns were used in the murders of 33 people in Britain, 36 in
Sweden, 97 in Switzerland, 128 in Canada, 13 in Australia, 60 in Japan and
13,220 in the United States." [New York Times, March 2, 1994]
Klaus Kassner
STUART P. BEATON wrote:
>
> Let me clarify - I assumed an unopened can at thermal equilibrium. If you
> open it, you destroy the equilibrium between the gas above the soda and the
> gas dissolved in it - that's why you see bubbles rising in an open
> container but not in a sealed one >which has had time to build up the
> pressure again and return to equilibrium<. I can certainly believe that
> shaking a de-pressurised bottle would encourage equilibrium by producing
> more nucleation sites.
>
I just tested this with a couple of bottles of mineral water (with gas).
One was unopened (you can tell from the seal): shaking it DOES produce
bubbles, and when you open it afterwards, you get lots of more bubbles.
The difference with a bottle that has been opened before (and closed again)
is that there are many more bubbles coming immediately when you shake the
latter (and they are smaller). The effect on opening afterwards was even more
pronounced than with the first bottle, but I am not sure whether this
is reproducible. It may depend on the initial degree of filling and the
age of the mineral water.
Bruce Bostwick
observations:
CO2 tends to dissociate at nucleation sites which in clean liquid are
typically on surfaces like the wall of the can. Tapping the can
dislodges the bubbles which then rise to the surface and merge with
the headspace. Thus less foam when the pressure is suddenly released.
The whole system is under 50-100 psig pressure (liquid and gas both!)
and when this pressure is released any bubbles in the liquid increase in
volume by 5-10 times. Watch the foam in the 3 liter bottle next time you
open it -- you'll see what I mean.
Reducing the pressure less gradually does seem to cause less dissociation.
I like my Coke pretty strong, so I like the slow venting techniques (it's
possible to *crack* the poptop seal and vent the pressure for 5-10 seconds
before fully opening..) It is sweeter flat; taking CO2 out of the solution
raises the pH and reduces the acid component of the flavor.
just my $.02 ...
<BGB> http://ccwf.cc.utexas.edu/~lihan/ mailto:li...@ccwf.cc.utexas.edu
Bruce Bostwick
Philip Gibbs <philip...@pobox.com> wrote:
>However, it certainly seems that bubbles dissipate in cola pretty
>quickly whether they are tapped or not. If the cans are left for
>just a short while after shaking they will not froth much in any
>case.
Actually, shaking doesn't really create actual bubbles, just vortices
which serve as additional nucleation sites if the pressure is let off
right away. If you leave the can sealed, they die down pretty quickly.
I have noticed a slight pressure rise in the aluminum cans after shaking,
but the difference in foaming is due to the greatly increased dissociation
rate rather than higher pressure. There is also a strong temperature
coefficient.
Bruce Bostwick
sbe...@du.edu (Stuart Beaton) wrote:
>One of Richard Feynman's books (I think it was) mentioned a demonstration
>that showed that the pressure in a can did _not_ increase upon shaking -
>and in fact there is no reason the CO2 should come out of solution.
Feynman also proved, and disproved, that an S-shaped nozzle underwater
would rotate in the opposite direction if you sucked the water into it
than it would if you pumped water out through it. He proved it and
disproved it so many ways, to the consternation of his fellow students,
that they did an impromptu experiment to check it empirically and in the
process blew up a 5-gallon carboy, which got them banished to the freshman
lab. He was fond of proving the ridiculous as an intellectual exercise ...
Triple Quadrophenic
In article <4oih5h$m...@nntp5.u.washington.edu>, fuji...@u.washington.edu
(Bryant Fujimoto) says...
>
>Frank_H...@sbphrd.com (Triple Quadrophenic) writes:
>
>>In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
>>(Stuart Beaton) says...
>>>
>>>
>>>that showed that the pressure in a can did _not_ increase upon shaking -
>>>and in fact there is no reason the CO2 should come out of solution.
>
>>preferably one that's had some removed. Open it up so that it's at
>>atmospheric pressure then put the lid on. If you squeeze the bottle now it
>>offers little resistance. Now shake the bottle and try squeezing again -
the
>>bottle will be much firmer.
>
>it come to equilibrium at atmospheric pressure before closing. That
>is you have to let the soft drink go flat. Then, if you close it and
>shake you will not get a significant change in pressure inside. If
>you don't wait, then when you close the top, the contents of the bottle
>are not at equilibrium, and shaking speeds the release of dissolved
>gases into the space above the liquid. After it reaches equilibrium,
>the situtation should be the same as before you opened it the first
>time, that is the pressure should not change if you shake the can or
>bottle.
>
Nope, If I let it equilibrate to 1 atm then there'll be virtually no CO2
left. Besides which a can of drink (which is what we're talking about here)
isn't flat.
OK. I've got a full 500ml clear plastic bottle of Pepsi Max sitting in front
of me (I was going to drink it for my coffee break bu I can make do with the
warm caffeine solution they call coffee here).
I'll leave it for an hour to equilibrate for an hour....
Right, lets squeeze the bottle. Hmmmm, estimated indentation (full force of
thumb) of 4mm.
Now for a good shaking -
Ooooh! Look at all those lovely bubbles that quickly form in the upper cm or
two of the coke, then swiftly move to the surface to form a foam.
Carefully note the huge numbers of bubbles that fail to stick to the sides
of the bottle (i.e., there are none on the side, whatsoever).
Lets try another squeeze of the bottle - Maybe a 1mm indentation. An obvious
increase in pressure.
>>I've encountered cans that I've been able to push in slightly before
opening
>>them. After a good shake they're as incompressible as ordinary cans.
>
>Can you suggest a reason why shaking a can should cause CO2 to leave
>solution? That is, why does shaking the can cause the contents of
>the can to shift from an equilibrium to a nonequilibrium condition?
>
Yes I can suggest a reason. However I see no need to. It doesn't matter what
the cause of it is, all you need to do is shake up a new, unopened,
see-through bottle of anything fizzy.
(OK, here's a possible reason. Shaking produces areas of varying presure in
the liquid. In the lower pressure areas the CO2 will come out of solution to
form tiny bubbles which act as nucleation sites. Have you ever looked at
liquids put into one of the sonic baths often used in laboratories for
cleaning glassware? Bubbles galore).
>Bryant Fujimoto
>fuji...@u.washington.edu
Jeremy M. Travins
Somewhere in this PILE of responses MUST lie the correct
answer...
MUST WE KEEP POSTING REPLIES TO THIS SUBJECT?
The topic has been sufficiently raped, beaten to death, and
then further mutilated...
Will this topic (along with the ever popular topic "Production
of Ice in the 1860's") get posted to some kind of science-FAQ's
link? If someone knows how to do it, please...
Bottoms up,
Jeremy
Robert Wiegand
DALE OLIVE <da...@kalama.doe.hawaii.edu> writes:
>As a science teacher I've done this as a demo many times and get about a
>90-95% success rate! I think the reason why I do get failures is because
>I haven't tapped the top hard enough! It doesn't matter how hard you
>shake it as I usually ask a student to do the shaking for me and they live
>for my failures . . .fortunately, for me, I usually dissappoint them!
>try it . . .I usually use a ruler to tap the sides and top . . .and keep a
>towel handy for those 5-10%.
Unless you also try opening cans without tapping and keep track of the
results over many trials this "demo" isn't demonstarating anything.
In fact it's an example of the wrong way to do an experiment.
There should always be a control.
>One of my favorite pressure demos is the "Alka-rocket" which I invented a
>few years ago. Take a "clear - fuji" film cannister and make a rocket
>out of it by taping an index card to the annister and affixing a index
>card nose cone on that. Put a teasppon of water in the cannister and one
>alka-seltzer tablet. Put the lid on quickly and place lid side down on
>the ground. In about 15 seconds enough pressure builds p to shoot the
>rocket 15-20 feet or more into the air. Try it , it works!
More like "reinvented". I had a toy like this about 30 years ago.
It does work great.
--
----------------------------------------------------------------------------
Bob Wiegand | Education makes a people easy to lead, but
Motorola Inc. | difficult to drive; easy to govern, but
bwie...@sesd.cig.mot.com | impossible to enslave - Henery Peter Brougham
Mike Schneider
> Can you suggest a reason why shaking a can should cause CO2 to leave
> solution? That is, why does shaking the can cause the contents of
> the can to shift from an equilibrium to a nonequilibrium condition?
>
CO2 + H2O --> Carbonic Acid
...has something to do with this.
Keep your stick on the ice,
Mike Schneider http://www.bae.umn.edu/Staff/schneider.html
STUART P. BEATON
Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
: > > 1) Does tapping the can after it has been shaken stop it from frothing
: > > when opened?
: OK, I'm back. To all you proponents of the tapping school, sorry, I'm
: just not seeing what you're seeing.
: Here's what I did. I got two 12-oz. aluminum cans of Coca-Cola Classic
: that had been sitting in the case at room temperature (currently 74
: degrees F) for a week. I simultaneously shook both with a vigorous
: longitudinal motion (in my less mature days I would have described
: this as hand job style) 60 times. Then I set both cans on the concrete
: pavement out back and immediately tapped one can 30 times around the
: top rim with a 12" length of metal conduit. Then I popped the tops of
: both cans simultaneously. There was no noticeable difference in
: fizziness.
: I repeated the process, this time tapping one can in the center of the
: lid for good measure in addition to around the rim. Again, no noticeable
: difference.
Your delay between shaking and opening may have been long enough to allow
the utapped can to defizz. Try this if you're willing to sacrifice another
couple cans: after shaking both cans, had one to an 'assistant' (this will
make sure that no vibrations from tapping will reach the control can), tap
your a couple times (~ 1 second), wait a second (allowing bubble to rise to
top), then open both. This will more closely approximate how it is done in
practice.
The scientific community awaits your results!
Stuart Beaton
sbe...@du.edu
J Scripko & N Greger
wpen...@interaccess.com (William R. Penrose) wrote:
>In article <4oi9eg$k...@neon.house.gov> "bb...@hr.house.gov (or) br...@lee.house.gov" <bb...@hr.house.gov> writes:
>>I remember when I was in high school, I used to work at
>>a grocery store. When Coke's delivery truck would come,
>>this guy at my job would throw up a can and then hit it
>>with a baseball bat. Then, the can would fly through the
>>air and hit the ground with an bang.
>I once saw a case of pop cans fly off a truck and scatter on the ground. As
>the other traffic hit the cans, it made a sound like a small war.
I once saw a beer truck dump a load of Molson's near a dorm in Ann
Arbor (U of Michigan) ... the students made a sound like a small
war... ;-)
Jim Scripko
Bill Nelson
Triple Quadrophenic (Frank_H...@sbphrd.com) wrote:
: In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
: >
: >
: >One of Richard Feynman's books (I think it was) mentioned a demonstration
: >that showed that the pressure in a can did _not_ increase upon shaking -
: >and in fact there is no reason the CO2 should come out of solution.
: I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
: preferably one that's had some removed. Open it up so that it's at
: atmospheric pressure then put the lid on. If you squeeze the bottle now it
: offers little resistance. Now shake the bottle and try squeezing again - the
: bottle will be much firmer.
This is not a realistic test, as you have not let it equalize again.
: I've encountered cans that I've been able to push in slightly before opening
: them. After a good shake they're as incompressible as ordinary cans.
I just tried this with 6 cans of Classic Coke, just a few minutes ago.
The result was, to my uncalibrated thumb, no noticeable difference.
I did not try tapping any, then opening them. If it had been Pepsi, I would
have done so - Pseudo-Coke is expendable for such trivial experiments. Coke
is not.
Bill
Jackee
In my personal experience, if I have dropped a can of coke
cola I always tap on the top prior to opening and have never
had one spue on me. If someone brings me a can of pop and
I suspect they have shaken it, I also do the same. This
mainly applies to my nephew, kids are good for such things
as shaking a coke.
If choose to respond please e-mail just passing through
looking for an article I heard about.
Jacke
adh...@scc-uky.campus.mci.net
_____ __ _
|__ |_______ _______| | / |______ ______
| | _ | ____| |/ /| _____| _____|
_____| | _ | |____| __ \| ____|| ____|
|________|__| |__|_______|__| \__|______|______|
adh...@scc-uky.campus.mci.net
Stuart Beaton
In article <31ADFB...@Physik.Uni-Magdeburg.de>, Klaus Kassner
<Klaus....@Physik.Uni-Magdeburg.de> wrote:
Yes, when you shake an unopened bottle you will see bubbles - It gos back
to what has been said before, that the gas in the headspace gets mixed
(temporarily) into the liquid. The point was that bubbles are not
_continuously_ formed, as they are in an opened container. Try this: take
one of your bottles, open it and add more water so there is no headspace,
then reseal and wait, say a day, for equilibrium to be re-established. Now
shake and see how many bubbles you get. (You may still get some headspace
formed as it pressurizes, and so a few bubbles from it)
Stuart
sbe...@du.edu
JUD MCCRANIE
: >> > 1) Does tapping the can after it has been shaken stop it from frothing
: >> > when opened?
I believe it does help to tap the top of the can. I haven't
done an A-B test, but I have observed for 20 years. It seems to
me that a can is significantly less likely to spurt out if the
top of the can is tapped before pulling the tab.
Jud McCranie jud.mc...@swsbbs.com
* Silver Xpress V4.3 SW20178
hello
When I worked for the City a streetsweeper guy said he hit a case of cokes
with his sweeper and it sounded like explosions underneath. They were on
the freeway in a hot Texas sun and he couldn't stop.
Ron Knight
Missed the original post, so I'm using "K. Murray"
<kmu...@emory.edu>'s quotation of it. But K. Murray didn't say
anything below.
|"Edward F. Zotti" <ezo...@merle.acns.nwu.edu> wrote:
|>It is commonly believed that if a can of soda pop you are about to
|>drink is shaken up first, you can keep the fizz from exploding out
|>when it's opened by first tapping around the rim of the can.
Well, you certainly know that if you open up a carbonated-beverage
container *while* shaking it up, you produce a great offensive weapon.
Solutions of carbon dioxide are pretty unstable, and agitation is
one thing that can cause the carbon dioxide to pass out of solution.
One thing that works in the other direction is pressure, and in a
sealed container, the pressure of the carbon dioxide in the air space
at the top will keep the dissolved CO2 from passing out of solution.
Therefore shaking up a sealed container runs up against a limit in
how much this will cause the CO2 to pass out of solution; the system
reaches equilibrium when the pressure of the CO2 in the air space
equals the pressure of the CO2 attempting to escape from solution.
After shaking stops the liquid will still slosh around for a while
inside the can, thus maintaining for a while the increased pressure
of the CO2 attempting to leave the solution. Whether or not there is
increased pressure due to agitation or heat or the air space is at
normal pressure this pressure is still greater than atmospheric
pressure, which causes the usual outflow of CO2 when the container
is opened. However, if the container has been agitated, waiting
until the liquid has stopped moving will decrease the pressure of
the CO2 attempting to leave solution, and even allow CO2 in the
air space to redissolve in the liquid, thus reducing the pressure
released when the container is opened. All this verbiage leads
to possible explanation #1 as to why tapping on the can might
actually keep it from exploding:
1) Even though the tapping itself accomplishes nothing, the time
delay between agitation and opening the container, caused by tapping
the can, allows the liquid to settle and reduces the pressure in
the container.
Possible explanation #2 actually posits some benefit to tapping
the can, since in agitating the can some of the liquid might be
spread across the inside top of the can. If all the liquid is
in the bottom of the can, and only CO2 in the top of the can, then
opening the can will pose little danger whatever the pressure
inside is (within normal conditions, of course): only dry CO2 will
escape, and that won't hurt anything.
(Well, actually, I guess we have to admit that just as there is
CO2 dissolved in the liquid at the bottom of the can, there is
liquid dissolved in the CO2 at the top of the can, and this will
liquefy under the reduced pressure when the can is opened. Thus
it is nearly impossible to completely prevent spray. But neglecting
that and getting back to the argument:)
If there is liquid adhering to the top of the inside of the can, then
it stands to reason that more liquid will spit out when the can is
opened, thus leading to reason #2 why tapping the top of the can might
actually be of use:
2) Tapping the top of the can knocks off the liquid adhering to the
top inside of the can so that there will be no liquid around the
opening when it is opened, and therefore the explosion will be
harmless dry CO2 rather than CO2-propelled beverage.
Herewith for your perusal, two possible reasons why tapping the top
of the can to avoid messy explosions may not actually be baseless.
Take it easy,
--
Ron "Tap my head before it explodes" Knight
(r...@med.unc.edu)
The University of North Carolina at Chapel Hill
I can't speak for UNC-CH, and UNC-CH can't speak for me.
It's better for both of us.
MoonRat
In article <Pine.PMDF.3.91.9606040...@MHFP.SWMED.EDU>,
hello <fp...@MHFP.SWMED.EDU> wrote:
>When I worked for the City a streetsweeper guy said he hit a case of cokes
>with his sweeper and it sounded like explosions underneath. They were on
>the freeway in a hot Texas sun and he couldn't stop.
>
>on Fri, 31 May 1996, J Scripko & N Greger wrote:
>
Why is this on soc.culture.native?
--
*****************************************************SsS*******************
MoonRat. The Ultimate Coffee fiend!!!! | |>
"Get that blood out of my caffeine stream!" ---
E-Mail: ur...@midway.uchicago.edu
Charles Bishop
In article <4ofccr$8...@news.acns.nwu.edu>,>jason...@gecm.com wrote:
>>
>> We have a man who is willing to shake a can for 10 seconds, and then tap
>> for 30 seconds, and then open the can in his face, as he is that
>> confident that it works. I will post the results of this experiment when
>> available.
>>
>Now we're talking. Could you post a .GIF? Also, in the interest of
>scientific thoroughness, perhaps you could post the temperature of
>the can. My experience has been that you can shake up a cold can of
>pop quite a bit without necessarily getting an explosion when you
>pop the lid--which may be why this myth persists. The real acid test
>would be shaking up a warm can. -Ed
Also, when you do the expt. Shake a similar can, let it sit for 30
seconds and then open it. All other conditions being equal. Repaet
5? times.
Charles, it's MY law, Bishop
Carl J Lydick
In article <4ofsrm$6...@homer.alpha.net>, sa...@ren.glaci.com (Trinlay Khadro) writes:
=Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
=: It is commonly believed that if a can of soda pop you are about to
=: drink is shaken up first, you can keep the fizz from exploding out
=: when it's opened by first tapping around the rim of the can. I have
=: been asked to venture an opinion on the usefulness of this procedure.
=: I am inclined to think it's a crock but would rather have scientific
=: backing before saying so in public.
=
=IMHO and not at all scientific, is that Tapping the can makes the person
=feel like they are doing SOMETHING while they wait.
= the "fizz explosion" will settle down if one waits before opening
=the container and opens it carefully.
= (tapping also keeps their hands on the can that needs to be
=opened carefully so they don't forget.)
Tapping the can can also dislodge bubbles from the side of the can, allowing
them to coalesce at the top. And compressed CO2 at the top of the can isn't
going to eject much liquid.
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: CA...@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL
Disclaimer: Hey, I understand VAXen and VMS. That's what I get paid for. My
understanding of astronomy is purely at the amateur level (or below). So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it. If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.
Carl J Lydick
In article <4ofm9g$p...@news.aladdin.co.uk>, tony...@aladdin.co.uk (tonywilk) writes:
=<g...@chem.duke.edu> wrote:
=
=>the physics theory that I know says that most of the bubbles form
=>after the can is opened because of the sudden lowering of pressure.
=>Tapping can't roosen bubbles that haven't formed yet. So I doubt
=>that the technique works. Just a typical superstition.
I don't suppose it occurred to you to try shaking a bottle of soda, now did it?
Nah, of course not. Shaking the soda DOES produce bubbles. These bubbles will
serve as good sites for outgassing once you lower the pressure.
Matt Klein
In <4pf9qs$s...@gap.cco.caltech.edu> ca...@SOL1.GPS.CALTECH.EDU (Carl J
I've heard/seen/found that tapping at or near the top does, as said
above, near nothing, but flicking the sides a few times should do the
trick.
Matt Klein
Joe Bramblett
On 28 May 1996 04:27:52 GMT, "Edward F. Zotti"
<ezo...@merle.acns.nwu.edu> wrote:
>One more thing. Warm pop that has been shaken up and then opened
>fizzes a lot more than cold pop. Is this purely a consequence of
>Charles' law? If so, would chilling be a good way to forestall a
>geyser next time you drop a warm can of Jolt?
>
>Replies by e-mail appreciated. For a newspaper column. -Ed
Don't know about that tapping thing, but if you can get me a list of
places in the Dallas area that carry Jolt, I'll think really nice
things about you. :-)
Thanks
Joe Bramblett
rtb...@airmail.net
Internet America
Airnews Project Manager
Carl J Lydick
In article <4oh3c1$8...@phunn1.sbphrd.com>, Frank_H...@sbphrd.com (Triple Quadrophenic) writes:
=In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
=(Stuart Beaton) says...
=>
=>
=>One of Richard Feynman's books (I think it was) mentioned a demonstration
=>that showed that the pressure in a can did _not_ increase upon shaking -
=>and in fact there is no reason the CO2 should come out of solution.
=
=I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
=preferably one that's had some removed. Open it up so that it's at
=atmospheric pressure then put the lid on. If you squeeze the bottle now it
=offers little resistance. Now shake the bottle and try squeezing again - the
=bottle will be much firmer.
I'm afraid your proposed experiment doesn't address the question. Outgassing
of the CO2 is *NOT* instantaneous. For your experiment to be valid, you'd need
to let the bottle sit until the pressure inside stopped changing.
Richard J. Green
In article <4pgb3l$e...@gap.cco.caltech.edu>,
Carl J Lydick <ca...@SOL1.GPS.CALTECH.EDU> wrote:
>In article <4oh3c1$8...@phunn1.sbphrd.com>, Frank_H...@sbphrd.com (Triple Quadrophenic) writes:
>=In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
>=(Stuart Beaton) says...
>=>
>=>
>=>One of Richard Feynman's books (I think it was) mentioned a demonstration
>=>that showed that the pressure in a can did _not_ increase upon shaking -
>=>and in fact there is no reason the CO2 should come out of solution.
>=
>=I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
>=preferably one that's had some removed. Open it up so that it's at
>=atmospheric pressure then put the lid on. If you squeeze the bottle now it
>=offers little resistance. Now shake the bottle and try squeezing again - the
>=bottle will be much firmer.
>
>I'm afraid your proposed experiment doesn't address the question. Outgassing
>of the CO2 is *NOT* instantaneous. For your experiment to be valid, you'd need
>to let the bottle sit until the pressure inside stopped changing.
Isn't it the case that coke is a supersaturated solution of carbonic
acid? At thermodynamic equilibrium with the atmosphere the coke will go
flat. I would think that the chemical potential of CO2 in the gas phase
would therefore be less than in the liquid phase. It seems thne that we
have a kinetic issue. Perhaps shaking the coke increases the _rate_ at
which equilibrium is achieved (don't ask me why?).
Regards,
Rich Green
--
----------------------------------------------------------------------------
Richard J. Green Dept. of Chemistry
r...@lyman.Stanford.EDU Stanford University
http://www-leland.Stanford.EDU/~redcloud Stanford, CA 94305-5080
"I've never been lost, but I've been confused for weeks on end."
-John Muir
Eric Gindrup
Richard J. Green wrote:
[...]
> Isn't it the case that coke is a supersaturated solution of carbonic
> acid? At thermodynamic equilibrium with the atmosphere the coke will
> go flat. I would think that the chemical potential of CO2 in the gas
> phase would therefore be less than in the liquid phase. It seems thne
> that we have a kinetic issue. Perhaps shaking the coke increases the
> Richard J. Green Dept. of Chemistry
> r...@lyman.Stanford.EDU Stanford University
> http://www-leland.Stanford.EDU/~redcloud Stanford, CA 94305-5080
> "I've never been lost, but I've been confused for weeks on end."
> -John Muir
I would suspect that the act of shaking the can produces small vortices.
They would be ideal nucleation points for the rapid formation of CO_2
bubbles. These vortices probably have short lifetimes. Hypothesis:
1) tapping the can wastes enough time for the vortices die down;
2) tapping the can disrupts the vortices and reduces the number of viable
nucleation points.
I don't find Feynman's experiment (I haven't *really* looked, but I
didn't find it with a little paging through some indices.), but would be
surprised to find that the pressure of gas over the Coke would change on
shaking. I would believe that the can becomes more incompressible
because the nucleation points provide excellent sources to replace CO_2
that is forced back into solution. Therefore, I would believe that the
reported experiment from Feynman was correct and that the observation of
more rigid shaken cans was correct.
The question of this thread seems related to a High School physics
experiment in which a can of Coke is placed in a freezer until it
explodes. The explosion is a result of removing energy from the Coke,
not putting energy in. However, the effect in both cases is to make the
liquid more susceptible to bubble formation. In the freezer, the liquid
is more likely to spontaneously generate bubbles from defects in the can
(which are somewhat rare) and random motions in the fluid. When shaken,
the liquid is more likely to generate bubbles because the tiny vortices
serve as nucleation points.
The real experiment would seem to take two cans of Coke (putatively
equivalent), shake both equally, place both on identical surfaces, tap
one without disturbing the other, open both cans, wait (oh, I suppose)
one second, seal both cans (separately), and measure the gas pressure
over each of them. If the pressures are different, it will indicate
which of tap or leave it alone is more efficacious. If the pressures
agree, then we know that tapping won't hurt and will give us some thing
to do while we wait for our Coke's vortices to die down.
-- Eric Gindrup ! gin...@okway.okstate.edu
may...@wkuvx1.wku.edu
> Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
> It is commonly believed that if a can of soda pop you are about to
> drink is shaken up first, you can keep the fizz from exploding out
> when it's opened by first tapping around the rim of the can. I have
> been asked to venture an opinion on the usefulness of this procedure.
> I am inclined to think it's a crock but would rather have scientific
> backing before saying so in public.
If the hypothesis is that tapping makes enough of a difference to be
easily observed without special equipment, the experiment seems
straightforward enough for a 12-year-old to do.
In fact, years ago my son did it for a school science project.
I held the stop watch. He varied the shaking times, the tapping
times, and the wait time before opening the cans. Controls were
handled similarly with no tapping, and controls were selected randomly
and announced at the end of the shaking. Fizz was measured (a) subjectively
by a fizz scale developed during several pre-experiment trials, and (b)
by the measured quantity of liquid expelled. Only a single brand of
generic cola was used. The experiment was conducted at approximately
refrigerator temperature on a winter day with the cans left outside
for a few hours to reach equilibrium temperature.
Result: The tapping made no grossly observable difference.
Regards,
Larry Mayhew may...@wkuvx1.wku.edu
B L David
Mr Tonywilk,
>=>the physics theory that I know says that most of the bubbles form
>=>after the can is opened because of the sudden lowering of pressure.
unopened coke can, then the vibration could cause the can to
explode? I expect that the can temperature would have to be
preset.
>=>Tapping can't roosen bubbles that haven't formed yet. So I doubt
>=>that the technique works. Just a typical superstition.
With a use of a high pitch sound, tapping might not be needed.
In a worst case scenario, the sound could come in proximity
to a truck loaded with coke.
-B David (bb...@hr.house.gov)
My views, not my employers
Carl J Lydick
In article <4photg$k...@d31rz2.Stanford.EDU>, r...@d31rz2.Stanford.EDU (Richard J. Green) writes:
=In article <4pgb3l$e...@gap.cco.caltech.edu>,
=Carl J Lydick <ca...@SOL1.GPS.CALTECH.EDU> wrote:
=>In article <4oh3c1$8...@phunn1.sbphrd.com>, Frank_H...@sbphrd.com (Triple Quadrophenic) writes:
=>=In article <sbeaton-2805...@sl-48.ducomm.du.edu>, sbe...@du.edu
=>=(Stuart Beaton) says...
=>=>
=>=>
=>=>One of Richard Feynman's books (I think it was) mentioned a demonstration
=>=>and in fact there is no reason the CO2 should come out of solution.
=>=I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
=>=atmospheric pressure then put the lid on. If you squeeze the bottle now it
=>=offers little resistance. Now shake the bottle and try squeezing again - the
=>=bottle will be much firmer.
=>
=>I'm afraid your proposed experiment doesn't address the question. Outgassing
=>of the CO2 is *NOT* instantaneous. For your experiment to be valid, you'd need
=>to let the bottle sit until the pressure inside stopped changing.
=
=Isn't it the case that coke is a supersaturated solution of carbonic
=acid? At thermodynamic equilibrium with the atmosphere the coke will go
=flat. I would think that the chemical potential of CO2 in the gas phase
=would therefore be less than in the liquid phase. It seems thne that we
=have a kinetic issue. Perhaps shaking the coke increases the _rate_ at
=which equilibrium is achieved (don't ask me why?).
That would be the obvious hypothesis: That shaking the bottle doesn't affect
the equilibrium pressure, but that if you open then reseal the bottle, without
shaking afterward, it can take quite some time for equilibrium to be achieved,
while shaking results in reaching equilibrium quickly.
David Pledger
Fun thread - here's my $0.02 worth...
Does shaking a can increase the pressure inside? Yes AND No.
Does tapping the can reduce fizz? Yes
P | * * * * * * * *
R | * *
E | * *
S | * *
S | * *
U | * *
R | * *
E | * *
| * *
+----------------------------------------------------
^ TIME ^
| |
+-- Can/bottle sealed. +-- Can/bottle opened
I suspect that shaking a bottle that was recently opened will increase the
pressure. The pressure will naturally increase until it reaches an
equilibrium point inside the bottle. Shaking the bottle accelerates the
rate at which it heads towards equilibrium by helping the gas to escape from
the liquid more quickly. Once equilibrium is reached, shaking has no effect
on the internal pressure. See graph. One could argue that shaking adds a
small amount of energy to the mixture which could temporarily change the
equilibrium point, but I believe this would have a negligible effect.
I also believe that tapping the can works. Tapping will help release any
bubbles that are attached to the sides of the can. Tapping will also buy a
little time allowing the bubbles to surface naturally. Fizzing originates
from two sources ... (1) Bubbles trapped below the surface of the liquid
when the can is opened. The volume of space occupied by a bubble is
inversly proportional to the pressure in the can (pv=nrt). When the can is
opened, the pressure decreases resulting in the volume of the bubbles
increasing. This sudden increase in volume causes fizzing. (2) Some CO2
may immediatly come out of solution when the can is opened, again due to the
pressure change. This may also cause fizzing. Tapping the can can only
relieve fizzing caused by #1.
So there you have it. Fun thread!
: =>One of Richard Feynman's books (I think it was) mentioned a demonstration
: =>that showed that the pressure in a can did _not_ increase upon shaking -
: =>and in fact there is no reason the CO2 should come out of solution.
: =
: =I'm certain that's wrong. Try it with a plastic bottle of fizzy drink -
: =preferably one that's had some removed. Open it up so that it's at
: =atmospheric pressure then put the lid on. If you squeeze the bottle now it
: =offers little resistance. Now shake the bottle and try squeezing again - the
: =bottle will be much firmer.
: I'm afraid your proposed experiment doesn't address the question. Outgassing
: of the CO2 is *NOT* instantaneous. For your experiment to be valid, you'd need
: to let the bottle sit until the pressure inside stopped changing.
--
+==============================+=============================================+
| David W. Pledger | S T R A T E G I C D A T A S Y S T E M S |
| dav...@lexis-nexis.com | PO Box 498, Springboro, OH 45066 |
| Custom Database Applications | Phone: (800)253-5624 ext 2940 |
+==============================+=============================================+
Eric Lucas
Interesting data. But this is of course done under the least favorable
conditions to observe anything. The cold and constant temperatures
assure maximum thermodynamic solubility of CO2, and minimal rate of
outgassing. If you think about when you're most likely to do this in
reality, it's in the summer at a picnic, when the soda is warming up
because it's been taken out of the fridge and is sitting ill-cooled in a
styrofoam cooler. In my observation, under those conditions (very cold
soda), little foaming results under any conditions. When I worry is when
the soda is beginning to approach room temperature and it somehow gets
shaken.
In addition, foaming is well-known to depend on solution surface tension.
You may have just chosen a brand of cola that has low surface tension and
therefore foams little. Root beer would be better because of it's well-
known foaming. Of course, *real* beer itself would be best, but then it
wouldn't be and experiment "straightforward enough for a 12-year-old to
do" (at least not anywhere in the US)! hee hee
Eric
William S. Lawson
The inside of a coke can is in thermodynamic equilibrium, witht the
amount of dissolved CO2 being appropriate for the pressure in the can
(and vice versa). It is not stable for lack of nucleation centers.
To make it explode you would have to heat it to where the equilibrium
pressure of the CO2 is great enough to explode the can -- probably not
a whole lot easier than just boiling the water in the coke.
Bottom line: a coke can next to the piano is no reason to call the
bomb squad.
(And can we show a little more self-discipline over cross-posting?)
-- Bill Lawson
Phil Boyd Studge
> Mr Tonywilk,
>
> >=>the physics theory that I know says that most of the bubbles form
> >=>after the can is opened because of the sudden lowering of pressure.
>
> So if you, instead, release a certain high-pitch sound around an
> unopened coke can, then the vibration could cause the can to
> explode? I expect that the can temperature would have to be
> preset.
>
> >=>Tapping can't roosen bubbles that haven't formed yet. So I doubt
> >=>that the technique works. Just a typical superstition.
>
> With a use of a high pitch sound, tapping might not be needed.
> In a worst case scenario, the sound could come in proximity
> to a truck loaded with coke.
> -B David (bb...@hr.house.gov)
> My views, not my employers
Actually one of the many *secret* projects the Nazi's were working on at
the end of the second world war was the use of intense sound to act as a
weapon. I also
see at one of the USArmy's web sites that some of their experimental
weapons programs have looked at this in the last few years...try searching
under sound weapons army or infrasound or some such combination of key
words at the www.altavista.digital.com web site.
Regards,
PBStudge
may...@wkuvx1.wku.edu
In article <31BF85...@peabody.sct.ucarb.com>, Eric Lucas <aea...@peabody.sct.ucarb.com> writes:
> may...@wkuvx1.wku.edu wrote:
>>
[...]
>> Result: The tapping made no grossly observable difference.
[...]
> Interesting data. But this is of course done under the least favorable
> conditions to observe anything. The cold and constant temperatures
> assure maximum thermodynamic solubility of CO2, and minimal rate of
> outgassing. If you think about when you're most likely to do this in
> reality, it's in the summer at a picnic, when the soda is warming up
> because it's been taken out of the fridge and is sitting ill-cooled in a
> styrofoam cooler. In my observation, under those conditions (very cold
> soda), little foaming results under any conditions. When I worry is when
> the soda is beginning to approach room temperature and it somehow gets
> shaken.
(1) There was plenty of fizzing. Cans that were opened
immediately after shaking spewed liquid all over my son, who was
opening them at arm's length. There was also quantitative data
(good bit of liquid missing from can) but I no longer have it.
(2) A picnic might be the most likely place for you to do it, but in
my son's peer environment (school), just-out-of-a-vending machine was
the most likely environment. Recall that this thread began about a widely-
accepted "rumor" that tapping makes a difference. This rumor, as I've
heard it over the years, has no qualifications about whether tapping
works on soda from a vending machine. The qualifications always begin
after one cites some actual evidence. Then it turns out that almost
anything might make a difference: phase of the moon (I kid you not),
whether one _believes_ in tapping, temp., brand, etc. It's gotten
to the point that, whenever this question arises, I mention our
experiment just to see if I'll ever get any experimental evidence
back. It hasn't happened yet. It has increased my respect for
experimental physicists, who must surely sometimes feel like trout
trying to swim up a waterfall. :)
> In addition, foaming is well-known to depend on solution surface tension.
> You may have just chosen a brand of cola that has low surface tension and
> therefore foams little.
It would have been disingenous of me to report no difference from
tapping if the truth were that there was little foam under any
circumstances. Still, I suppose the cola we used could have been
contaminated with something that produced hallucinations of fizzing
when there was none. ;-)
> Root beer would be better because of it's well-
> known foaming. Of course, *real* beer itself would be best, but then it
> wouldn't be and experiment "straightforward enough for a 12-year-old to
> do" (at least not anywhere in the US)! hee hee
Ha! And best of all would be a new rumor: If you tap on a beer before
drinking it, it won't make you drunk! That hypothesis strikes me as
robust enough to resist a great deal of contrary evidence. :)
Regards,
Larry Mayhew may...@wkuvx1.wku.edu
MikeTEACHR
I wonder what the average psi is for a nice warm shaken coke can, and
also, what the average burst pressure for coke cans. mike
Greg Trayling
pbst...@cris.com (Phil Boyd Studge) wrote:
> ... (deletorama)
>
>Actually one of the many *secret* projects the Nazi's were working on at
>the end of the second world war was the use of intense sound to act as a
>weapon. I also
>see at one of the USArmy's web sites that some of their experimental
>weapons programs have looked at this in the last few years...try searching
>under sound weapons army or infrasound or some such combination of key
>words at the www.altavista.digital.com web site.
>
mine used to claim). The idea was to find a resonance frequency for various
internal organs. Jolting someone's kidneys around is apparently very
uncomfortable.
\________/ _________ ___________
/\______/\_/ Web Warrior / ______/\ /___ ____/\
/ /\____/\ _ Tra...@uwindsor.ca / /\_____\/ \__/ /\___\/
/ / /\__/\/ / / / / ___ / / /
_/_/_/_/\/\- \_\___ http://www.cs.uwindsor.ca/meta-index/people/traylin
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\/______\`============================================\\^7^^^^^^^^^^^'
/ \ \/
Bob Shepherd
In article <Dszqu...@news.uwindsor.ca>,
Greg Trayling <tra...@server.uwindsor.ca> wrote:
... (deletorama)
>>Actually one of the many *secret* projects the Nazi's were working on at
>>the end of the second world war was the use of intense sound to act as a
>>weapon. I also
> The British were also working on a similar project (or so an old prof of
>mine used to claim). The idea was to find a resonance frequency for various
>internal organs. Jolting someone's kidneys around is apparently very
>uncomfortable.
If you want to find the exact frequency ask my neighbor.
He likes to play that station on his stereo now and then. :-O
Bob Shepherd
Eric Gindrup
Phil Boyd Studge wrote:
[...]
> Actually one of the many *secret* projects the Nazi's were working
> on at the end of the second world war was the use of intense sound
> that some of their experimental weapons programs have looked at
> this in the last few years...try searching under sound weapons
> army or infrasound or some such combination of key words at the
> PBStudge
Or equivalently, look at the Borland Turbo C++ online help for sound() or
beep().
-- Eric Gindrup ! gin...@okway.okstate.edu
(It refers to a setup where a chicken farm was located next to a
facility producing sounds of the resonant frequency of chicken
crania. Quite humorously told.)
James Michael
>
> The British were also working on a similar project (or so an old prof of
>mine used to claim). The idea was to find a resonance frequency for various
>internal organs. Jolting someone's kidneys around is apparently very
>uncomfortable.
>
>
I thought it was the resonance frequency of the anal sphincter, so that
everybody at a riot would loose control and generally loose interest. It
was a low frequency.
Jim
Malcolm Jussawalla
Matt Klein (m...@ix.netcom.com) wrote:
: In <4pf9qs$s...@gap.cco.caltech.edu> ca...@SOL1.GPS.CALTECH.EDU (Carl J
: Lydick) writes:
: >
: >In article <4ofsrm$6...@homer.alpha.net>, sa...@ren.glaci.com (Trinlay
: Khadro) writes:
: >=Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
: >=: drink is shaken up first, you can keep the fizz from exploding out
: >=: when it's opened by first tapping around the rim of the can. I have
: >=: been asked to venture an opinion on the usefulness of this
: procedure.
: >=: I am inclined to think it's a crock but would rather have
: scientific
: >=: backing before saying so in public.
: >=
: >=IMHO and not at all scientific, is that Tapping the can makes the
: person
: >=feel like they are doing SOMETHING while they wait.
: >= the "fizz explosion" will settle down if one waits before opening
: >=the container and opens it carefully.
: >= (tapping also keeps their hands on the can that needs to be
: >=opened carefully so they don't forget.)
: >
: >Tapping the can can also dislodge bubbles from the side of the can,
: allowing
: >them to coalesce at the top. And compressed CO2 at the top of the can
: isn't
: >going to eject much liquid.
: I've heard/seen/found that tapping at or near the top does, as said
: above, near nothing, but flicking the sides a few times should do the
: trick.
:
: Matt Klein
I tap the bottom 3 times and it works!
--
"Those who make no mistakes, never make anything." By Some Guy.
GO ARGOS GO BLUE JAYS GO MAPLE LEAFS GO RAPTORS GO!
LIVE LONG AND PROSPER!
E-mail North America bu...@torfree.net
John Price
Contrary to the later responses, all variables of importance seem to be,
well, ok as far as control.
Personally, I think this rumor had its origins in the world of beer and
champagne. Here, tapping the sides of a freshly poured glass is thought
to decrease the head of both. The proposed mechanism is that the
vibrations caused by the tapping alters the bubbles to the point that
they break.
may...@wkuvx1.wku.edu wrote:
:
: > Edward F. Zotti (ezo...@merle.acns.nwu.edu) wrote:
: > It is commonly believed that if a can of soda pop you are about to
: > drink is shaken up first, you can keep the fizz from exploding out
: > when it's opened by first tapping around the rim of the can. I have
: > been asked to venture an opinion on the usefulness of this procedure.
: > I am inclined to think it's a crock but would rather have scientific
: > backing before saying so in public.
:
: If the hypothesis is that tapping makes enough of a difference to be
: easily observed without special equipment, the experiment seems
: straightforward enough for a 12-year-old to do.
:
: In fact, years ago my son did it for a school science project.
: I held the stop watch. He varied the shaking times, the tapping
: times, and the wait time before opening the cans. Controls were
: handled similarly with no tapping, and controls were selected randomly
: and announced at the end of the shaking. Fizz was measured (a) subjectively
: by a fizz scale developed during several pre-experiment trials, and (b)
: by the measured quantity of liquid expelled. Only a single brand of
: generic cola was used. The experiment was conducted at approximately
: refrigerator temperature on a winter day with the cans left outside
: for a few hours to reach equilibrium temperature.
:
: Result: The tapping made no grossly observable difference.
:
: Regards,
: Larry Mayhew may...@wkuvx1.wku.edu
--
John M Price, PhD jmp...@calweb.com
Laterality Laboratory jmp...@ucdavis.edu
Human & Community Development jmp...@worldnet.att.net
University of California, Davis
thamlk
>the end of the second world war was the use of intense sound to act as a
>weapon. I also
>see at one of the USArmy's web sites that some of their experimental
>weapons programs have looked at this in the last few years...try searching
>under sound weapons army or infrasound or some such combination of key
>words at the www.altavista.digital.com web site.
>
>
>PBStudge
I remember hearing in the news that the US have in fact gotten their
"sonic tech" to work...they concentrate more on the amplitude of the
sound though. Well, if you think about it, sound being a longitudinal
waveform will cause vibrations in any medium it encounters. So you could
in fact have a 200dB sound at less than 20Hz, the low threshold of human
hearing, or conversely have one at more than 20kHz, the high threshold.
So an inaudible sound at 200dB could become a high tech "humane"
weapon...
By the way, 200dB is enough to cause considerable vibration of body
tissues, esp. those in the body cavity, to cause extensive organic damage
to cells, blood vessels, and other tissues, and thus is sufficient to
KILL...
-Douglas Tham
tha...@temasek.teleview.com.sg
thamlk
Bill Nelson
Eric Gindrup (gin...@okway.okstate.edu) wrote:
: (It refers to a setup where a chicken farm was located next to a
: facility producing sounds of the resonant frequency of chicken
: crania. Quite humorously told.)
Which, of course, is myth. Calculate the frequency for a sound wave
in air of about 1 inch, and you will see why.
Bill
Scott Cutler
In an issue of Popular Science (I believe the article was "Softkill"),
they were describing ways of disabling troops. One of the ways was to
project very low frequency sound waves at the troops, and depending on
the levels, disable them by interfering with their balance and making
them go nauseous. Sounds fun.
Scott Cutler SCu...@ix.netcom.com
Eric Gindrup
Hmm... Lessee... 300 m/s * ~30 in/m / 1 in ~= 9 kHz. Doesn't seem
*that* ridiculous...
Yaakov Eisenberg
In article <31C5D4...@okway.okstate.edu>,
Eric Gindrup <gin...@okway.okstate.edu> wrote:
* Bill Nelson wrote:
* >
* > Eric Gindrup (gin...@okway.okstate.edu) wrote:
* >
* > : (It refers to a setup where a chicken farm was located next to a
* > : facility producing sounds of the resonant frequency of chicken
* > : crania. Quite humorously told.)
* >
* > Which, of course, is myth. Calculate the frequency for a sound wave
* > in air of about 1 inch, and you will see why.
* >
* > Bill
*
* Hmm... Lessee... 300 m/s * ~30 in/m / 1 in ~= 9 kHz. Doesn't seem
* *that* ridiculous...
* -- Eric Gindrup ! gin...@okway.okstate.edu
That's close to the frequency mentioned in the story:
True story: 7 Hz is the resonant frequency of a chicken's
skull cavity. This was determined empirically in Australia,
where a new factory generating 7-Hz tones was located too
close to a chicken ranch: When the factory started up, all
the chickens died.
(from the Turbo C++ v1.01 Library Reference, in the entry for nosound())
--
-Yaakov Eisenberg (yaa...@cc.gatech.edu)
Michael Edelman
Yaakov Eisenberg (yaa...@cc.gatech.edu) wrote:
: That's close to the frequency mentioned in the story:
: True story: 7 Hz is the resonant frequency of a chicken's
: skull cavity. This was determined empirically in Australia,
: where a new factory generating 7-Hz tones was located too
: close to a chicken ranch: When the factory started up, all
: the chickens died.
That pretty much reads as nonsense.
A chicken's skull cavity would have a resonant frequency of more like
a few kilohertz at least. 7Hz would require something the size of
an elephant's skull.
Plus, the skulls are usually filled with chicken brains. ;-)
--mike
adam
On 19 Jun 1996 04:04:04 -0400, yaa...@cc.gatech.edu (Yaakov Eisenberg)
wrote:
>In article <31C5D4...@okway.okstate.edu>,
>Eric Gindrup <gin...@okway.okstate.edu> wrote:
>* Bill Nelson wrote:
>* >
>* > Eric Gindrup (gin...@okway.okstate.edu) wrote:
>* >
>* > : (It refers to a setup where a chicken farm was located next to a
>* > : facility producing sounds of the resonant frequency of chicken
>* > : crania. Quite humorously told.)
>* >
>* > Which, of course, is myth. Calculate the frequency for a sound wave
>* > in air of about 1 inch, and you will see why.
>* >
>* > Bill
>*
>* Hmm... Lessee... 300 m/s * ~30 in/m / 1 in ~= 9 kHz. Doesn't seem
>* *that* ridiculous...
>* -- Eric Gindrup ! gin...@okway.okstate.edu
>
>That's close to the frequency mentioned in the story:
>
> True story: 7 Hz is the resonant frequency of a chicken's
> skull cavity. This was determined empirically in Australia,
> where a new factory generating 7-Hz tones was located too
> close to a chicken ranch: When the factory started up, all
> the chickens died.
>
Hmmm, does anyone know the resonant frequency of a human's skull
cavity? :)
gl...@glass.cv.lexington.ibm.com
In <4q91mv$j...@cwis-20.wayne.edu>, m...@pookie.pass.wayne.edu (Michael Edelman) writes:
>Yaakov Eisenberg (yaa...@cc.gatech.edu) wrote:
>
>: That's close to the frequency mentioned in the story:
>
>: True story: 7 Hz is the resonant frequency of a chicken's
>: skull cavity. This was determined empirically in Australia,
>: where a new factory generating 7-Hz tones was located too
>: close to a chicken ranch: When the factory started up, all
>: the chickens died.
>
>
>A chicken's skull cavity would have a resonant frequency of more like
>a few kilohertz at least. 7Hz would require something the size of
>an elephant's skull.
>
>Plus, the skulls are usually filled with chicken brains. ;-)
>
>--mike
Err, elephant skulls are usually filled with elephant brains, not
chicken brains :-)
Dave
P.S. Sorry, I couldn't resist.
Robert Griego
James Michael wrote:
> >
>
> > The British were also working on a similar project (or so an old prof of
> >mine used to claim). The idea was to find a resonance frequency for various
> >internal organs. Jolting someone's kidneys around is apparently very
> >uncomfortable.
> >
> >
>
> I thought it was the resonance frequency of the anal sphincter, so that
> everybody at a riot would loose control and generally loose interest. It
> was a low frequency.
>
> Jim
According to urban legend, 13 Hz should do the job.
--
Robert Griego <>< Texas Instruments Incorporated
#include <disclaimer.h>
"By definition, risk-takers often fail. So do morons.
In practice it's difficult to sort them out."
--Scott Adams
Richard J. Green
In article <31C9A5...@ti.com>, Robert Griego <rgr...@ti.com> wrote:
>James Michael wrote:
>>
>> Greg Trayling <tra...@server.uwindsor.ca> wrote:
>> >pbst...@cris.com (Phil Boyd Studge) wrote:
>> >> ... (deletorama)
>> >
>>
>> > The British were also working on a similar project (or so an old prof of
>> >mine used to claim). The idea was to find a resonance frequency for various
>> >internal organs. Jolting someone's kidneys around is apparently very
>> >uncomfortable.
>> >
>> >
>>
>> I thought it was the resonance frequency of the anal sphincter, so that
>> everybody at a riot would loose control and generally loose interest. It
>> was a low frequency.
>>
>> Jim
>
>According to urban legend, 13 Hz should do the job.
I'm sure glad it's not 10 Hz (the rep. rate of my YAG).
:-)
Regards,
Rich Green
--
----------------------------------------------------------------------------
Richard J. Green Dept. of Chemistry
r...@lyman.Stanford.EDU Stanford University
http://www-leland.Stanford.EDU/~redcloud Stanford, CA 94305-5080
"Remember the days of yore,
"Learn the lessons of the generation that came before you."
-Deuteronomy 32:7
Trinlay Khadro
gl...@glass.cv.lexington.ibm.com wrote:
: Err, elephant skulls are usually filled with elephant brains, not
: chicken brains :-)
Uhh, kinda off topic to the message but not the header...
is there a reason why people are feeling so agressive to
canned Coca Cola of late?
I think this is the second rather long running abuse
of canned soda-pop threads....
Michael Edelman
gl...@glass.cv.lexington.ibm.com wrote:
: >That pretty much reads as nonsense.
: >
: >A chicken's skull cavity would have a resonant frequency of more like
: >a few kilohertz at least. 7Hz would require something the size of
: >an elephant's skull.
: >
: >Plus, the skulls are usually filled with chicken brains. ;-)
: >
: >--mike
: Err, elephant skulls are usually filled with elephant brains, not
: chicken brains :-)
: Dave
: P.S. Sorry, I couldn't resist.
Forgiven. And then there are those heads filled with dancing saucers
and sugarplum faeries....
--mike
Michael Edelman
Richard J. Green (r...@d31rz0.Stanford.EDU) wrote:: >>
: >> > The British were also working on a similar project (or so an old prof of
: >> >mine used to claim). The idea was to find a resonance frequency for various
: >> >internal organs. Jolting someone's kidneys around is apparently very
: >> >uncomfortable.
: >> >
: >> I thought it was the resonance frequency of the anal sphincter, so that
: >> everybody at a riot would loose control and generally loose interest. It
: >> was a low frequency.
: >>
: >> Jim
: >
: >According to urban legend, 13 Hz should do the job.
: I'm sure glad it's not 10 Hz (the rep. rate of my YAG).
Welll...it may depend on size ;-)
Tesla did a lot of VLF experiments. He had visitors (including Mark Twain)
stand on a plate attached to a pneumatic oscillator he disigned that
would oscillate large objects (like buildings!) at their resonant
frequencies. One side effect, it was reported, was the loss of bowel
control!
This is documented in "Tesla: Man Out Of Time", a fun read.
--mike
Lenny Nero
m...@pookie.pass.wayne.edu (Michael Edelman) wrote:
>--mike
I really loved that book and still am amazed at the fact that
scientists have yet to figure out what the heck tesla actually was
doing :) .
-Dan
Eric Lucas
Actually, Mike, I think the appropriate rejoinder might have been "so's
yours!" hee hee. (Sorry, Dave, I couldn't resist either. ;^) )
Cheers,
Eric