Science question

SixPapaCharlie

SixPapaCharlie

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If I put mentos in diet coke, it doesn't change the pressure in the bottle, it only accelerates the release of gas since adding a mentos doesn't actually add any more carbon dioxide to the solution.

All it is doing is releasing the same amount of gas, just expediting it.
We're all on board there right?

Now when I shake a plastic bottle of coke, I am also not adding anything to the solution.
Same amount of gas, same amount of liquid.

However, I can certainly feel the bottle expanding and seemingly the pressure increasing.

If the number of molecules is static, why am I able to feel or perceive an increase in the pressure?
 
Aren't you taking the CO2 from liquid to gaseous form, which in a sealed container, causes an increase in pressure due to the expansion necessary when converting to gas?
 
Those molecules only exert gas pressure as they come out of solution.


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SixPapaCharlie said:
If I put mentos in diet coke, it doesn't change the pressure in the bottle, it only accelerates the release of gas since adding a mentos doesn't actually add any more carbon dioxide to the solution.

All it is doing is releasing the same amount of gas, just expediting it.
We're all on board there right?

Now when I shake a plastic bottle of coke, I am also not adding anything to the solution.
Same amount of gas, same amount of liquid.

However, I can certainly feel the bottle expanding and seemingly the pressure increasing.

If the number of molecules is static, why am I able to feel or perceive an increase in the pressure?
Click to expand...

Conservation of mass (and matter) not volume.

Why does frozen or vapor H2O take up more volume than liquid?
 
Possibly you are accelerating the disolving and reaction by shaking!
 
1 mole of gas takes up 22.4L at standard temperature and pressure. I guess you're taking CO2 out of solution and releasing it in gaseous form.
 
SixPapaCharlie said:
If I put mentos in diet coke, it doesn't change the pressure in the bottle, it only accelerates the release of gas since adding a mentos doesn't actually add any more carbon dioxide to the solution.

All it is doing is releasing the same amount of gas, just expediting it.
We're all on board there right?

Now when I shake a plastic bottle of coke, I am also not adding anything to the solution.
Same amount of gas, same amount of liquid.

However, I can certainly feel the bottle expanding and seemingly the pressure increasing.

If the number of molecules is static, why am I able to feel or perceive an increase in the pressure?
Click to expand...

CO2 is supersaturated in the can, so shaking it will accelerate the time to reach saturation. Its like flying through a cloud and getting wet.
 
The CO2 in a soft drink is not simply in solution like N2 would be. If you put pressurized N2 over your beverage, a small quantity will dissolve into the space between molecules in the beverage, and when you remove pressure, most of it will come out as fine bubbles you probably won't notice, since there really isn't that much dissolved that way.

With CO2, that same first stage happens, but then a second stage happens. The dissolved CO2 reacts with water to become carbonic acid. As time passes, more of the pressure over the liquid passes through these two stages, until the pressure reaches an equalibruim between the pressure in the bottle, and the undisturbed state of carbonic acid.

However, carbonic acid isn't that stable. If you shake the container, it tends to disassociate back to water and CO2, and raise the pressure in the can.

If you have a bottle that has not recently been agitated, and you open the lid, releasing the pressure, the CO2 that is dissolved that is in excess of what the new, lower pressure is, will bubble out. And the carbonic acid that is in excess of the current pressure equilibrium will start to disassociate and bubble out. But in the absence of mechanical agitation or mechanical impurities, it is a slow process. Often, you will see a glass with specific points where the carbonation is bubbling off of continuously. These are nucleation sites. Something mechanical, likely a sharp spot in the glass, or a piece of grit stuck to the side of the glass is serving as a mechanical accelerator for disassociating the carbonic acid.

It just happens that the make up of mentos is rich with mechanical structure that works as a nucleation site for disassociating carbonic acid. So instead of a glass with maybe dozens of nucleation sites, you've dropped in an object with maybe tens, or hundreds of thousands of nucleation sites, and the conversion of carbonic acid to CO2 goes much faster.
 
Jack Turner???!!!! I thought your dad instructed you not to play with his computer or his PoA account.
 
Pressure.

By taking the co2 out of solution, you are moving it into gaseous form and creating a pressurized gas in the head space of the bottle. That gas pushes against the non compressible liquid and transfers it’s force to the liquid. It is a basic hydraulic air/liquid interface.

The strength of the pressure on the side of the bottle equals the pressure in the head space x the surface area of the neck of the bottle where gas meets liquid.

Sorry if that is a boring answer.
 
flhrci said:
What about BBQ science?
Click to expand...
That's as much art as it is science.

Although there is the guy who started the American Royal BBQ contest (in KC, the largest BBQ contest in the world). He goes by the name "Remus Powers, PhB". The degree was conferred by Greasehouse University.
 
Are you an actual scientist, or do we need to pay cash under the table for this information?
 
-KLB- said:
The CO2 in a soft drink is not simply in solution like N2 would be. If you put pressurized N2 over your beverage, a small quantity will dissolve into the space between molecules in the beverage, and when you remove pressure, most of it will come out as fine bubbles you probably won't notice, since there really isn't that much dissolved that way.

With CO2, that same first stage happens, but then a second stage happens. The dissolved CO2 reacts with water to become carbonic acid. As time passes, more of the pressure over the liquid passes through these two stages, until the pressure reaches an equalibruim between the pressure in the bottle, and the undisturbed state of carbonic acid.

However, carbonic acid isn't that stable. If you shake the container, it tends to disassociate back to water and CO2, and raise the pressure in the can.

If you have a bottle that has not recently been agitated, and you open the lid, releasing the pressure, the CO2 that is dissolved that is in excess of what the new, lower pressure is, will bubble out. And the carbonic acid that is in excess of the current pressure equilibrium will start to disassociate and bubble out. But in the absence of mechanical agitation or mechanical impurities, it is a slow process. Often, you will see a glass with specific points where the carbonation is bubbling off of continuously. These are nucleation sites. Something mechanical, likely a sharp spot in the glass, or a piece of grit stuck to the side of the glass is serving as a mechanical accelerator for disassociating the carbonic acid.

It just happens that the make up of mentos is rich with mechanical structure that works as a nucleation site for disassociating carbonic acid. So instead of a glass with maybe dozens of nucleation sites, you've dropped in an object with maybe tens, or hundreds of thousands of nucleation sites, and the conversion of carbonic acid to CO2 goes much faster.
Click to expand...
Soooo... Magic? Joking aside, cool to read your post. I learned stuff.

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SixPapaCharlie said:
If I put mentos in diet coke, it doesn't change the pressure in the bottle, it only accelerates the release of gas since adding a mentos doesn't actually add any more carbon dioxide to the solution.

All it is doing is releasing the same amount of gas, just expediting it.
We're all on board there right?

Now when I shake a plastic bottle of coke, I am also not adding anything to the solution.
Same amount of gas, same amount of liquid.

However, I can certainly feel the bottle expanding and seemingly the pressure increasing.

If the number of molecules is static, why am I able to feel or perceive an increase in the pressure?
Click to expand...

Because the CO2 is dissolved in the liquid and not in gas form.
 
Yes, the bottle gets "hard" because the CO2 comes out of solution (whether by shaking or by having mentos added to form nucleation sites). Eventually, if you leave it sealed, it will go back into solution.
 
Here's the classic experiment...

 
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