Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from a release of the gas. An everyday example is seen in carbonated beverages such as soft drinks. The visible bubbles are produced by effervescence from the dissolved gas (which itself is not visible in the liquid solution).
In the laboratory, a common example of effervescence is seen if hydrochloric acid is added to a block of limestone. If a few pieces of marble or an antacid tablet are put in hydrochloric acid in a test tube fitted with a bung, effervescence of carbon dioxide can be witnessed.
- H2CO3 → H2O + CO2