I Didn’t Know That...

Q: Why does a bottle of soda or carbonated water sometimes freeze after it is opened?

*

A: One common way to prevent water from freezing is to dissolve something in it. This is one reason why salt is spread on icy roads in winter. Dissolved carbon dioxide will have the same effect. If a bottle of soda is cooled below 32 degrees Fahrenheit, it can remain liquid because of the dissolved gas. But opening the bottle allows carbon dioxide to escape, and crystals of ice can form in the supercooled water. High pressures also prevent water from freezing because ice is less dense than water. So some of the freezing impetus comes form lowering the pressure inside the bottle.