You might notice a person buy soda or a beer can and tapping it on the top before opening it. We all have seen our elders doing so to prevent the carbonated drink from fizzing over and have followed suit without questioning the validity of the trick.
The Chemistry Professor at the Nottingham Trent University, Chris Hamlett explained the science of tapping soda can before opening it.
Hamlett started off by explaining the foaming process in the carbonated beverages and the origin of the ‘hissing’ sound when a can is opened:
“The refreshing ‘hiss’ is the result of gas bubbles escaping from the liquid as a result of a change in the solubility of the carbon dioxide (CO2) in it.”
The solubility of carbon dioxide changes due to the pressure change as the carbonated drink is opened. On opening the soda can, the pressure decreases and the tiny bubbles lining inner side of the unopened can grow larger.
“When these bubbles reach a certain size, they detach from the inside of the can and rise up to the top of the can due to buoyancy and displace liquid in their path.”
So, does Tapping the can Help?
Taping the can clears the path by pushing the gas bubbles aside. However, HowStuffWorks maintains that one cannot be sure if tapping on the top of the sealed can dislodges enough gas bubbles to prevent the drink from fizzing over! If the drink has recently been shaken, it is best to let sit for a while before opening the can.
Or you can skip the waiting and brace yourself as the drink hits you in the face!