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Post by ozboomer on Jul 16, 2016 7:34:39 GMT -5
Nothing at all to do with musical things... but an observation that is confusing me (of little brain)...
Dad will open a bottle of lemonade (or soda, for our friends across the mighty Pacific), pour himself a drink and twist the cap back on the bottle... but not very tightly (he is 95, after all).
After 20 minutes or so, he'll go back to the bottle (whether it's in the 'fridge or out in the open doesn't seem to make any difference) and try to open it and the cap will be stuck on so hard that he can't take it off. I'll sometimes also have trouble getting it removed.
Now, I looked-up the old Chemistry books and refreshed my memory about Charles' Law, Boyle's Law and even Gay-Lussac's Law... but they don't explain what's happening with the silly bottle cap.
I'm curious to know if any of my esteemed Dedicated Followers of Physics (Chemistry) have any suggestions??
Ta...
John
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Post by newey on Jul 16, 2016 11:19:46 GMT -5
Here's my best-guess answer, as a total layperson. This, therefore, could be completely wrong.
The soda is infused with carbon dioxide gas (I assume your "lemonade" is carbonated, no?). The amount of gas that can exist, in suspension, in the liquid, is dependent upon the air pressure in the bottle; that pressure is likewise pushing down upon the surface of the soda, just as it is against the sides of the bottle and against the cap. The bottler "saturates" the soda with CO2; the liquid can't hold any more without outgassing.
When full, that cap is "factory-sealed", and there is very little airspace in the bottle. Some, not much, of the gas gets exhausted into the air at the top of the bottle, which is why you hear a "pssshhhh" when you twist it open for the first time. But, mostly, the CO2 stays put, dissolved in the liquid.
Then, you open it, release the pressure, and pour a glassful, then recap the bottle. There is now considerably more airspace in the top of the bottle, and less pressure upon the surface of the liquid. The liquid can't hold the same amount of CO2, so it outgasses into the air at the top of the bottle, increasing the air pressure inside. This, then, pushes against the cap, making it harder to twist off.
This is similar to the away that the amount of water vapor that can be suspended in air is dependent upon the barometric pressure. And, that's why we should all call "fake" during those airliner-disaster movies, where the plane experiences a rapid depressurization. First thing that happens when you depressurize an airliner at about 30,000 feet is that you've made the world's greatest fog machine. All the moisture in the air precipitates out at once with the rapid pressure drop as the air can no longer hold that amount of water vapor. But, a pea soup fog in the fuselage would ruin the movie's obligatory horror shots of the passenger's expressions . . .
The fact that your elderly father doesn't put it on very tightly? Well, he's putting it on tightly enough to seal it. The caps generally have a plastic "gasket" on the inside- that means one doesn't have to twist it very tightly to seal it.
Anyway, that's my story until someone with some actual physics comes along.
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Post by sumgai on Jul 16, 2016 11:51:13 GMT -5
newey's post above hits on all cylinders, but there is a bit more.
A pressure differential is indeed part of the trick, but combined with that is the fact that the bottle cap would not be able to hold at all, and still be removable, if it weren't for the fact that that "plastic" ring (a sealing washer) reacts with the gasses to distort a bit, and thus form a tight seal. A torsional force will disturb that seal, but not a tensional force. However, as the amount of room for the remaining liquid to outgas is much higher, the sealing washer now will have a much stronger reaction, which in turn means an even tighter seal that the original (when shipped).
The proof of this would be simple: don't recap the bottle for half an hour or so. Allow any outgassing to occur, then put the cap back in place. In an hour or so, try uncapping the thing... it was much easier, no? Sadly, the "fizz factor" was also destroyed, so this procedure is "for experimental purposes only", you understand. 
HTH
sumgai (Who was into Chemistry, until he was shocked to discover Electricity at about 11 years of age. Boy did he love all that smoke and stink - almost as much as the sparks and melted metals!) |
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Post by ozboomer on Jul 16, 2016 20:30:03 GMT -5
Ahhhh, excellent...! Much good-thinkin' goin' on here... as always  Heh.. I might be a silly ol' ginger-beer... but sometimes there's very much a "can't see see the forest for the trees" -thing going on... and I just need to have my thinkin' nudged in a different direction. Now, 'tis just to work out how to deal with the problem for dear ol' Dad... when I'm not around, anyway. ..but, from what has been suggested, to be able to get the cap off, the fizz needs to go, which sorta defeats the point of having the fizz in the drink in the first place... Pffft! Fanx! a heap, folks... John |
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Post by gumbo on Jul 17, 2016 3:40:32 GMT -5
"......Now, 'tis just to work out how to deal with the problem for dear ol' Dad... when I'm not around, anyway...." Buy him a pair of multigrip pliers....  ...glad I could help! g-f-b |
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Post by sumgai on Jul 17, 2016 18:55:57 GMT -5
^^^^^ Somebody slap me if I'm wrong, but did I just see a g-f-b post that was not a derailment?  |
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Post by gumbo on Jul 18, 2016 2:08:28 GMT -5
.....sorry ...I'll have to be more careful....  |
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Post by newey on Jul 19, 2016 11:11:46 GMT -5
On a semi-related topic, when one uncorks a bottle of champagne, it must be consumed relatively quickly, lest it lose its fizz. And there is no good way to re-cork the bottle But my parents would place a spoon, handle end first, into the neck of the bottle of bubbly. They both swore that this preserved the carbonation much longer. I now do the same, and it does seem to keep the bubbles much longer, although I haven't done any empirical testing. It makes no sense that it should work, but it seems to.
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Post by b4nj0 on Jul 19, 2016 13:50:29 GMT -5
My sister does that spoon "trick" too, but then she also has an unshakable faith in homeopathy.
Jury's out it seems, but until it returns my name has to be Thomas I'm afraid.
Slewing back a bit to the thread, PV=nRT. I understood that to be PV=mRT, where the R is the universal gas constant and m represents mol which has something to do with equivalence of molecular weight with something else that slips my mind after north of three decades. Is the use of n in the equation an American take on it? As is my custom, I quote from memory and not t'interweb, so it's not a rhetorical question, just brought back memories when I saw it that's all.
e&oe...
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Post by ozboomer on Jul 19, 2016 17:01:16 GMT -5
Slewing back a bit to the thread, PV=nRT. I understood that to be PV=mRT, where the R is the universal gas constant and m represents mol which has something to do with equivalence of molecular weight with something else that slips my mind after north of three decades. Well, I did my Chem/Physics school study in the mid-late '70s (Haliday & Resnick's "Physics" threw me for a major loop in 1st year of Civ Eng, talking about baryons, mesons, leptons, quarks... *erk*) ... studying from a "telephone book" (pre-publishing) manuscript of a (proposed) text book and THAT used the "n"... Heck, I remember wreckin' my back carrying that silly thing to and from school... Sheeesh... |
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Post by JohnH on Jul 19, 2016 17:52:46 GMT -5
An irrelevant but related factoid is about why Cork was ever used as a stopper for bottles?
The reason is, it is one of very few naturally occurring materials which has a negative Poissons ratio.
Poissons ratio relates to how much a material bulges out sideways when you squash it. Most materials have a positive value, such as rubber or metals, which get fatter under a compressive load.
So, a bottle stopper made of solid rubber is very frustrating, because when you push it, it expands further outwarda making it impossible to insert.
But cork, due to its unusual cellular structure, actually collapses inwards under compression. So pressing a cork into a bottle reduces its diameter making it possible to insert it. Once the compression is relieved, it expands out again, positively sealing the bottle.
Which does not help much when trying to get a Champagne cork back in, but at least helps to understand how it got there in the first place.
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Post by reTrEaD on Jul 19, 2016 22:51:43 GMT -5
Soft drinks get very sticky when the water evaporates, almost like glue. My first thought was some of the drink got on the threads of the bottle. But twenty minutes doesn't seem very long. Maybe ... idk. |
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Post by gumbo on Jul 20, 2016 6:51:32 GMT -5
I'd still go for the multigrips...  |
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Post by ozboomer on Jul 23, 2016 7:07:21 GMT -5
...and (sort-of) un-derailing this thread... ... "Curiouser and curiouser" --The Cheshire Cat, "Alice's Adventures in Wonderland" by Lewis Carroll The next installment... If you now take the lemonade bottle not long after it has become empty, fill it with water from the tap, place the cap on the top fairly tightly... and shake the bottle like crazy, you'll find the bottle starts to collapse; that is the, pressure inside the bottle is reduced to be lower than the atmospheric pressure. Open the bottle and you get the "Pffff" of the pressure equalizing... then empty the water out.. wait a few more minutes... and do it all again... and the bottle collapses again.. But! not as much. ..."'tis a puzzlement" (which I've quoted before, I believe). John |
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Post by sumgai on Jul 23, 2016 11:53:07 GMT -5
Temperature differences? |
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Post by cynical1 on Jul 23, 2016 17:03:31 GMT -5
Open the bottle and you get the "Pffff" of the pressure equalizing... then empty the water out.. wait a few more minutes... and do it all again... and the bottle collapses again.. But! not as much. ..."'tis a puzzlement" (which I've quoted before, I believe). This begs the obvious question, how many beers had you ingested before embarking on this line of experimentation? HTC1 |
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Post by ozboomer on Jul 23, 2016 17:38:31 GMT -5
Zero beers, acshually... I just have an inquirin' mind (as you well know) Just having tea (dinner)... and Dad has a preference for lemonade these days (being 95, he's gotta get most anything he wants, I reckon)... and we have the bottle on the table with us... and opening and closing the bottle prompted the first question and last night, the bottle was emptied and I was washing it out for the recycle bin.. and made this new observation... Always the engineer... even watching some NetFlix thingy on Algorithms last night, wotcha thin'!? John |
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