I Didn’t Know That . . .

Q: Why does shaking a can (or bottle) of soda (or champagne) increase the pressure inside so that soda sprays everywhere when the can is opened?

A: It doesn’t. Two chemists at the Australian National University in Canberra demonstrated that in 1988 by attaching a pressure gauge to a soda bottle and measuring the pressure before and after shaking. There was no change. Why then does the liquid spray out? Because shaking disperses the gas at the top of the can or bottle into little bubbles scattered throughout the soda. The tiny bubbles act as nucleating agents, sites where gas dissolved in the soda can escape, forming larger bubbles. When the can is opened, these bubbles try to escape, carrying liquid with them. If the can is allowed to sit for a while, the bubbles redissolve.