Why do styrofoam cups fizz more than plastic cups?

[utomg]

If you open a fresh bottle of soda pop and pour it slowly into a plastic cup it fizzes (effervesces) a little bit. If you pour it slowly into a styrofoam cup it fizzes a lot --- a whole lot!

Why?

Is it because styrofoam isn't smooth, so when the soda is poured in the CO2 is "shaken" loose against the rough edges?

Just wondering

utomg

[Ivar]

That's a pretty crude but correct way to describe it.

I'm sure someone will come along with a better explanation.

[Number]

Yep, the rough spots are called nucleation sites (http://www.straightdope.com/classics/a3_356b.html).

[vertigo]

I'm almost positive that is the reason. All the nooks and crannies in the styrofoam allow the CO2 a place to seed and then develop into bubbles big enough to break free and float to the surface and the cycle starts again.

In related way you can cause some serious burns by microwaving a cup or bowl of water in a very smooth container. Without any imperfections to seed the steam bubbles, the water can reach boiling without actually coming to a "boil". When moved or when a spoon is drop in it can explosively react and begin to boil. It can throw scalding water all over the place.

[Philster]

On a related note, why does diet soda fizz out fast and go flat faster?

Mild Hijack.

[psi724]

Just curious Philster, but have you actually timed this out or is it subjective?

It may have something to o with the chemical make up, the sugars in a "standard" soda being more likely to retain the CO2 in solution. It might be that the diet, has a lower boiling point. (I know I know, arguably the same thing, but not quite, one has to do with activity, the other entropy)

This is what I suggest:
1. Take your normal diet and nondiet sodas and look at the labels.
2. Compare ingredients.
3. Compare Nutrition facts (this can tell you about the make up of the soda, not very precisely but if you see that they have the same ingredients, but that the sugar in the nondiet soda is 10g more than the diet, that is an explanation)
4. Freeze them measuring the temperatures at which they become solid.
5. Boil them, see which boils first and at which temperature. The one that boils first from your statement above should be the diet.
6. Add a twist of lemon and maybe a shot of rum to the boiled Dr Pepper and enjoy.

Oh wait, that is just my prefered hot drink....

But that should help you with out starting down the chemical activities, entropies, and what not. FYI, I am a chem/bio engineer so if you want to we can go into it, but I am lazy and the explanations from the experiment would work more easily.

[psi724]

As you can see, I obviously spent too much time in the loabs and never took English courses.

[psi724]

"Me fail english!!! Thats unpossible!!!" - Ralph

[Philster]

psi724, as a fellow Philly Doper, you have to trust me.

Actually, diet soda goes flat faster, and I've timed it and measured the amount of bubbles after 1 minute. I mean, it's so obvious (the difference in bubbles) that my anecdotal evidence will have to suffice.

As you pour diet soda, regardless of brand, much of the carbonation is lost right after/during pouring. I avoid diet soda in 2 litre bottles because it doesn't have a chance of surviving the pouring process. I buy cans or small bottles only.

I guess it's time to boil them...

[psi724]

Interestingly enough from Coca-Cola...

"We do not monitor the exact freezing temperatures of each of our products. However, our diet products freeze at a temperature similar to water, 32 degrees. Coca-Cola classic freezes at a slightly lower temperature, about 30 degrees. The pressure in an unopened bottle or can will cause the freezing point to be even lower. All diet beverages will freeze before their sugar counterparts. Sugars lower the freezing point of liquids. This means that the temperature must get lower than the normal freezing point of water before it freezes."

This would imply that the classic should boil at a lower temp than the diet. Although, the sugar percentage may get in the way with that. So now we are back to the question of activity and what VanderWaals and Hydrogen Bonding may be taking place. Course it could just be a matter of solubility. Be back on that one.

[Philster]

Don't some 'additives" to water DECREASE the freezing point while SIMULTANEOUSLY RAISING the boiling temp? Antifreeze additives do both.

In the soda case, sugar would be the additive...it lowers the freezing temp and raises the boiling temp..

Doesn't salt do the same? Adding salt raises the boiling temperature, no? It lowers the freezing temp, we know that. I understood salt to raise the TEMP at which water boils.

So, sugary soda will freeze at a lower temp and boil at a higher one...??

[psi724]

I wonder (since I have no diet soda around me) if it has to do with the ingredients being phosphoric acid in classic and X and phosphoric in diet? I have no diet here but I am guessing that there is another acidic ingredient to help disolve the other stuff that is put in.

The following reactions take place with water & Co2:

CO2 (aq) + H2O H2CO3 (aq)
H2CO3 (aq) + H2O H3O+ (aq) + HCO3- (aq)
HCO3- (aq) + H2O H3O+ (aq) + CO32- (aq)

Normally, since the CO2 is coming out, the reactions naturally drift towards the CO2, and thus it comes out.

Seems to me that if there are too many donators of H to the place that it would drive the reactions towards CO2, thus more likely to "boil" completly out faster than standard. I am looking for data on solubility, but with out calculations I think it is hopeless. And like I already said, I am lazy today.

[Philster]

Aha...I just learned that any non-volatile soluble substance - like sugar - will raise the boiling point.

So, to help myslef, siince artificial sweeteners are 'sweeter' than sugar, by volume there is less sweetener in diet than regular soda, thereby causing regular sugary soda to have a higher boiling point because it has more soluble substance than diet.

[Philster]

But now I am confused because more sweetener should mean moe nucleation points???????

AHH!

(Thanks psi, for your crack at it...but I'm confused!)

[psi724]

I think that the salt thing you raised is not right. The salt raises the entropy:

dG=dH-TdS

No chemical reactions therefor dG=0

dH=TdS

At phase changes dH=H1-H2 = C

C=TdS

dS = Cpln(T2/T1)
dS = (Cp1 + Cp2 + ...) ln (T2/T1)

Since Cp(water) + Cp(anything) > Cp(water)
dS must increase.

If H = TdS and dS increases, then T must decrease.

Think about it this way, you put salt into water to make it easier to boi or to melt the icel, same thing as oil (depending on the type it will just break surface tension). There is not too much change but enough that it helps. To get it hotter, you cover it with the lid, thus increasing pressure, i.e. the pressure cooker.

As for the antifreeze, I think that the system is under pressure that does the trick, not that the antifreeze raises the boiling temp. Unless the additive has a higher boiling point than the water...

[psi724]

I realize that the formula dS = CPln(t2/T1) is a change in temp, and that at steady state (no dT) there is no change in dS but the principle still applies.

Also, the sweeteners are typically more swet than sugar, thus lee sweetener creating less nucleation sites. There for lower boiling point.

[Philster]

So why does diet soda go flat real fast?

My head hurts.

[psi724]

Has to do with my explanation on CO2 reactions above.

Summary:

1. Established that diet will boil at a LOWER temp. Thus less soluble with CO2 than nondiet. At boiliing temp for diet, nondiet will be still retaining CO2 whereas it will be boing off in the diet.

2. Possible more acid in diet sodas, thus causing more of a swing to CO2 in the reactions. More CO2 present, more that will come out.

3. Less possible activity and Hydrogen bonding etc between the
CO2 with the sweetening agent in diet than with sugar in nondiet. Thus more readily comes out in diet than non diet.

4. Boiled Dr. Pepper and lemon go good together.

Other than these, I would say that it is a factor of the coefficients of heat. Just guessing here, but diet might heat up faster than nondiet, thus releasing more CO2. Check that by timing the temperature rise between the 2 drinks.

And I was just determined to be a dork by my office for wondering and researching this.

[Ludovic]

Originally posted by psi724
I realize that the formula dS = CPln(t2/T1) is a change in temp, and that at steady state (no dT) there is no change in dS but the principle still applies.

Also, the sweeteners are typically more swet than sugar, thus lee sweetener creating less nucleation sites. There for lower boiling point.

Well, nucleation sites aren't molecular-sized phenomena (i don't remember if they are large microscopic phenomena or just tiny macroscopic, but larger than molecular-sized.)

[bbeaty]

Nucleation sites are called... BUBBLES. Carbon dioxide needs a gas/liquid interface if it's to come out of solution. If there aren't any tiny pre-existing bubbles, there will be no large bubbles. If you pour some cola into a styrofoam cup, the crevices provide trapped bubbles which grow and then break off, leaving a tiny bubble to repeat the process.

Stare into your beer. Those little spots which emit strings of bubbles are either air-filled scratches, or they are bits of air-filled filth which the dishwasher missed.

Good sources of large numbers of tiny bubbles: dry sugar, salt, powdered creamer or choclate. Melted ice cream. Dry, frosty ice cubes. Diluted (liquified) whipped cream. Water which has just had some dry powder added recently. Hot tap water (full of microbubbles.)

If you (sneakily) place any of the above materials into a glass and then let someone pour in a carbonated beverage, guess what happens?

Or: prepare two nearly-full glasses of root beer. Into one dump some milk. It turns beige, but that's all. Into the other pour some whipped cream which has been mixed with water to make it resemble milk. DOOSH! With an appropriate orifce attached to the root beer glass, you could make a rocket engine. Ah, try using a turkey baster to rapidly inject a large volume of dilute whipcream into a nearly-full 2L bottle of warm cola.

:)

PS If you have a mouthful of melted ice cream and then take a big swig of warm rootbeer, don't try to keep your mouth closed or the foam explosion will jet out of your nose.


FOLLOW THESE INSTRUCTIONS (See 'foam blast')
http://amasci.com/brain/

[bbeaty]

Hmmm. Wouldn't the higher viscosity of sugar-water make the bubbles grow more slowly? After all, the carbon dioxide molecules have to diffuse across quite a distance of liquid to arrive at the bubble surface. If the water is made more viscous, it should slow the CO2 diffusion and slow down the outgassing.

"Less fizz" has to involve either fewer bubbles or bubbles which grow more slowly. I bet it's the second one.

[hutchley]

Philster - on a similar subject, adding sugar to a cup of VERY hot coffee just removed from a microwave causes it to boil up and over the edge of the cup. I always assumed that this was because adding sugar LOWERED the bp of the coffee???

Have I been mistaken all these years??? Bummer.....

[hutchley]

bbeaty - is that along the lines of the 'impossible beverage', i.e. a guinness & coke?? Always a good one to ask for if you suspect the bartender is new in the job........stand well back.

[bbeaty]

Originally posted by psi724
4. Boiled Dr. Pepper and lemon go good together.


Ah, that explains the strange poster that was in the local burger joint back when I was a kid. It had a bunch of ski bunny types with steaming mugs, and a title "DR PEPPER, TRY IT HOT!"

[bbeaty]

Originally posted by hutchley
Philster - on a similar subject, adding sugar to a cup of VERY hot coffee just removed from a microwave causes it to boil up and over the edge of the cup. I always assumed that this was because adding sugar LOWERED the bp of the coffee???

Have I been mistaken all these years??? Bummer.....


Actually I found several "nucleation site" substances empirically while messing with superheated water & microwave ovens. Superheated water acts very much like warm cola.

http://amasci.com/weird/microexp.html#coffee

Any substance which carries microbubbles into the superheated coffee-water will trigger some explosive boiling. For instance, hot tap water would do it, but re-heated tap water would not. Put a little dish-soap into hot tap water, wait a few minutes, and you'll see a layer of white foam appear as the microbubbles rise to the surface. Let some hot tap water stand around for awhile and it loses its microbubble load, and it will no longer trigger boiling when dumped into superheated water.

Dry wooden coffee-stirrers (or toothpicks) will make your superheated water boil. They're like the "boiling stones" used by chemists to prevent explosive boiling. New clean glassware has too few scratches to offer trapped microbubbles.

Sugar crystals don't "wet" instantly, so they carry an air film. Same with salt, sand, powdered creamer, and dry frosty ice cubes. (Wet ice cubes won't trigger cola fizz.)

Try this: pour a lot of salt into a little water, stir so as much dissolves as possible, then dump it into cola. Big explosion of fizz. Then pour some salt into water, stir, let it stand for a half hour, then dump it into cola. FAR less fizz. By letting it stand you did nothing to the salinity, but you did let all the microbubbles rise to the surface. (I haven't tried it, but I bet if you kept stirring for the entire half-hour, the microbubbles would still be there, and the stuff would still make the cola fizz.)

[hutchley]

thanks bbeaty - that's one of life's little mysteries cleared up !!

Next time I'm at Muppet Labs (aka my kitchen....) I'll have to try a few of these for myself.

hutchley

[Popup]

In a similar vein (as the OP), there is a huge difference between clear plastic cups and white plastic cups. I believe that the white plastic cups have a rougher surface, and thus provide more nucleation sites than the clear variety, where a rough surface would be a whole lot more visible.

It is almost impossible to pour beer in a white plastic cup! It will foam and spill over at once if you're not carefull.

[Philster]

Flat diet soda: It's not my imagination and I'll have to learn to live with it (unless someday the artificial sweetener that replaces sugar is replacing sugar on a 1 to 1 volume basis, and has a similar affect as sugar, creating very similar boiling points between diet and regular. Until then, diet will fizz out faster than regular soda)

Thanks, all!

[psi724]

Ludovic and bbeaty, sorry for the nit-pic here (granted what I am talking about here is the 1 time in a billion billion billion and would always be overcome by simpler methods, aka dirt, but I will defend myself to the bitter end) but depending on the relative sizes of the molecules, nucleation can be considered microscopic. Also, yes, to come out of solution, there is a needed interface, however that does not exclude the interface creating itself, aka a brand new bubble. Pressure rerelated to bubble radius is:

P1-P1 = 2y/r

As you take r to 0 you see that the pressure difference required goes to infinity. Since there is not likely to be a non-chaos induced event like this, nucleation "must" occur for a bubble to form, which we are agreed upon. Of course that is assuming that y (surface tension) remains constant.

The question is what may act like a nucleation site. Since it is an assist to breaking the infinite pressure barrier, anything that creates a situation in which vapour formation occurs, leading to the formaion of a bubble can be defined as a nucleation site. In addition, the surface tension gives us some room to play. If an object (molecular or otherwise) i introduced that will lower y, this decreases the pressure required. Thus, a sugar/sweetener molecule that can act through molecular/ionic/anything else forces to seperate the water into gaseous phase would be a nucleation site.

That being said and argued, the most common reasons for nucleation are what you stated, air is trapped and diffusion of the gas into the air blah blah blah.

And good call bbeaty on the viscosity affecting diffusion and it also comes into play with my bubble formula. Although the question is, isn't the mass transfer of the eddying soda resulting from the pouring greater than the rate of diffusion?

Back to the OP with Popup, are the injection molds different for your cups? Also is the type (number) of plastic different? I am wondering if you had a clear #2 X type cup versus a colored #2 X type cup if there would be a difference........

[KellyM]

Diet soda has FAR less syrup than regular soda -- the calibration on diet taps in a soda fountain is significantly different.

The things you learn working at Pizza Hut.

[Philster]

Diet sode has no syrup, so that would qualify as far less.

[KellyM]

Philster, the stuff that is mixed in with the water and the carbon dioxide is still commonly called "syrup" even if it contains no actual sugar.