The trick to preparing the perfect pop, therefore, is to keep as much of this dissolved CO2 inside the liquid as possible. One way to do this is to refrigerate your soda as cold as possible, although you don’t want to freeze it. When soda is cold, the carbon dioxide molecules have less energy to escape, and cold soda can hold more CO2. That’s why soda that you buy cold will be fizzier than soda that’s been sitting unrefrigerated on the store’s shelves. Another strategy, which the soda bottler might do at the factory, is to load up the air at the top of the container with extra carbon dioxide, or increase the pressure of this gas. This will make it harder for the CO2 to escape, and also increase the rate at which these molecules are returned to the soda.