As you know, our bodies need oxygen and food. What you may not know is that we use oxygen in the chemical process that breaks down sugars in our cells to give us energy. Each cell in our bodies has little power plants called mitochondria (my toe KON dree uh) that basically burn sugar to make a form of energy that the cells can use. This process uses oxygen and makes water and carbon dioxide (CO2) as wastes. We get rid of water in a few ways, such as urinating, sweating, and even breathing it out.

We also breathe out carbon dioxide. When carbon dioxide mixes with water, it forms a weak acid called carbonic acid. Normally, this is not fizzy, but if you were exhaling into a basic (alkaline) solution, it might fizz.

When soft drink companies make fizzy drinks, they do it by injecting carbon dioxide into them. Thats why theyre called carbonated beverages. They have to do this under pressure, which forces the carbon dioxide gas to stay in the liquid. When you open a container of a carbonated drink, the pressure is released and the bubbles of carbon dioxide can escape. This kind of fizzing is not caused by acids and bases mixing, its just a gas escaping from a liquid. Why do you think fizzy drinks go flat when you leave them open?