Is carbonation an example of a chemical reaction?

No. Carbonation is simply dissolving carbon dioxide gas in a liquid. Only indirect chemical change occurs, and if you just let the carbonated liquid sit for a while, it will reverse itself. A chemical reaction involves the destruction and or formation of bonds, which does not occur during the carbonation proper. Thus carbonation is a physical change, not a chemical one.

However, under pressure, water and carbon dioxide form carbonic acid (H20 + CO2 -> H2CO3) which makes most carbonated beverages slightly more acidic. This change reverses itself when normal atmospheric conditions are restored.

Please see: http://en.wikipedia.org/wiki/Physical_change http://en.wikipedia.org/wiki/Chemical_reaction http://en.wikipedia.org/wiki/Carbonation