Science Buddies: "Ask an Expert"

Hi, for a grade 7 project, myself and my daughter did experiments to test whether squeezing a fizzy drink bottle after it was opened accelerate CO2 losses as compared to just closing it properly without squeezing it.
Our results showed that is was better to squeeze it.
I expected it to be worse when squeezed as more CO2 could escape.
Can someone please help us with the theory / explanation?

Hi ajbasson500,

In a full, unopened bottle of fizzy water, the pressure is relatively high. Opening the bottle releases some of the carbon dioxide and the pressure is reduced. Carbon dioxide pressure in a partially full bottle is reduced due to the lower volume of water (and greater “empty” volume). When you squeeze the drink bottle, the “empty” volume is decreased and the carbon dioxide pressure is increased. The solubility of carbon dioxide is greater at higher pressures. Thus more carbon dioxide stays in the water when the “empty” volume of the drink bottle is smaller (and the pressure is higher).

I hope this helps. Please ask again if you have more questions.

A. Norman