Shakes soda flat

Why doesn't soda go flat immediately after opening?

If you open the bottle and reduce the pressure, you now have a supersaturated solution of carbon dioxide in water, so it is energetically beneficial for the gas to leak out of the solution.

However, in order for the gas to exit the solution, a bubble must form, and the mechanism by which this occurs is known as nucleation. However, there is an energy barrier that prevents tiny bubbles from forming. As a result, bubbles will only form if there is something to help them nucleate. More about this at:

If you look closely at the bubbles from an opened bottle of soda, you will find that they do not form accidentally. You will usually see streams of bubbles from an area that is assisted in nucleation, e.g. B. a defect in the glass wall of the bottle.

This means that the escape of the gas involves two steps:

  1. Blistering on a core

  2. Diffusion of carbon dioxide through the water to the core

And it's step 2 where the carbon dioxide takes a while to escape. If there is some aid to nucleation, e.g. B. in the case of a defect in the glass wall, a bubble forms very quickly. However, the formation of the bubble quickly consumes the dissolved carbon dioxide in its vicinity and the formation of more bubbles must wait for more carbon dioxide to diffuse to the nucleation site. The diffusion of gases dissolved in water is surprisingly slow, and although the gases typically only need to diffuse a few millimeters, it still takes a while to do so.

If you want to get the carbon dioxide out quickly, it is best to increase the number of nucleation sites so that you get many more nuclei and thus reduce the distance the dissolved gas needs to diffuse. The traditional way to do this is to toss a mint in the bottle of soda, but if you do, take a good step back.

Nuclear Wang

How does mint increase the rate of germination? It sounds like the diffusion of CO2 through the water is the rate-limiting step. If the mint doesn't dissolve to create more uniform nucleation points, I don't see how the mint creates such an effervescence.

James

Interesting. If you've prevented nucleation, what is the upper limit for diffusion for STP? I wonder how slow the diffusion could be if we were to use a highly polished, non-reactive vessel. Would be a great product. The lemonade bowl! LOL -> physics.stackexchange.com/q/229684/96218

detly

@R .. Right off the bat I doubt it - all you would do would be through turbulence and deformation of the tank wall more creating potential nucleation sites (and that's if you can hard beat). But ask away!

Beanluc

Turbulence is exactly what is causing this. Not because it creates more nucleation sites, but because it creates more fluid flow over the already existing nucleation sites. As the liquid flows, the slowness of diffusion is less of an obstacle to nucleation.

Bilkokuya

@R .. When you open the can, any tiny bubbles at the nucleation sites expand quickly and float to the surface - squeezing any liquid over them as well. Tapping the can tries to push the bubbles off the sides of the can so that they rise to the top. When you open the can, less liquid will be pushed out.