Why Do People Tap on Cans?Answer: Tapping on the top of a carbonated beverage can (or bottle) before opening it may help prevent the drink from exploding out of the can upon opening (although it might not be sufficient!). Sparkling or carbonated beverages contain carbon dioxide gas that is dissolved in the liquid by pressurizing the contents of the can. When the can is opened, the mixture depressurizes and the carbon dioxide comes out of solution, escaping as carbon dioxide gas. If there is liquid between the gas bubble and the outside of the can, then some of the liquid may be pushed out of the can with the bubble. The pressure gradient when the can is opened is greatest near the opening and the carbon dioxide at the top of the can escapes first. If the can has been shaken, then the pressure differential inside the can during shaking will force some of the carbon dioxide out of solution to form bubbles. Some bubbles float to the top and some stick to the sides and bottom of the can. G