The Science behind soda eruptions

Have you ever tapped the top of your soft drink can before opening it to avoid the fizzy overflow? You may have been wasting your time; however, there are other ways to keep the fizz on the inside. Often , many people who drop their canned drinks on the floor tap the top of the can before opening to ensure they don’t mess themselves with the fizzy liquid once opened. 

 

Many of us out there have tried this in the past, thinking that this would “calm” the energised carbonated liquid before cracking open the can, however, scientific explanation demonstrations negative results to its contents. 

 

Chemistry experts on Reddit’s ‘ask science’ forum have been questioned by users such as Andrew3573: “It seems to have worked for me in the past, but I've heard from some people that it's just an urban legend?” 

 

Moderator “Crnaruka”, an expert from the forum explained that the results from tapping the can is almost negligible, and does nothing to prevent the fizzy drink gushing out, hence the above is most likely a myth. 

 

"The best you can do is simply to wait for the gas in the bubbles to settle back into the liquid," they add. This has to do with the "rate of nucleation, or bubble formation".

 

"Initially the CO2 in the liquid is supersaturated, which means that it wants to escape. However, before it can do so it needs to first form bubbles.

 

"The first step of bubble formation, the nucleation, can be fairly slow because it is an activated process, meaning that it needs to pass over an energy barrier, which we call the activation energy (Ea)." By shaking the can or dropping it on the ground, one provides enough energy to surpass this barrier, hence forming 1000’s of tiny bubbles while doing so. 

 

"Once you produce some bubbles, these bubbles will actually make it more likely for more bubbles to form (if you want to get technical, this is a process we call heterogeneous nucleation).

 

"This is why all hell breaks loose when you open a bottle after shaking it - the millions of tiny bubbles rapidly produce more bubbles and much of the CO2 trapped in the liquid rushes out, taking the liquid with it."

 

The best way to settle your can would be to simply wait for the gas in the form of bubbles to settle into a more restful state, or settle back into a solution. "At that point it will be as though you had never disturbed the can in the first place."

So basically, tapping your can does nothing much to change the equilibrium of the gas dissolved in the liquid and in the head-space.

 

But Crnaruka adds: "As for the idea that tapping the sides can dislodge part of the trapped bubbles and reduce the fizzing, I admit that this is more plausible. However, the evidence I've seen one way or another is all over the place, always anecdotal, and largely inconclusive".