Effervescence

This is the technical name for bubbling. Effervescence occurs when a gas is produced in a solution, and the bubbles of gas can be seen rising through the liquid. The reaction between an acid and sodium carbonate solution shows effervescence due to the production of carbon dioxide gas:

This is sometimes used as a test for acids.

Take care when making observations regarding effervescence. Students often squirt one solution into another, and see some bubbles. This is not surprising - it's simply air from some violent squirting! Make sure that bubbles of gas are actually being produced within the liquid. Also, look carefully - they may be quite small bubbles.