Entry by Meredith Duffy, AP225, Fall 2011
Supersaturation refers to a solution state that results from dissolving more solute in a solvent than its solubility limit would dictate for the given conditions. This is often achieved by dissolving solute in the solvent under one set of conditions, then altering those conditions (e.g. lowering the temperature) to get the same amount dissolved despite the solute's lower solubility under the new conditions. Supersaturated solutions are by definition unstable on their own, and just a slight change of conditions (the addition of impurities to serve as nucleation sites, for example) can result in precipitation of the supersaturated solid or, say, in the case of carbonated water, formation and release of supersaturated gas bubbles. However, various stabilizing methods have been developed to achieve a wide variety of supersaturations that are stable, at least on the short term (ex: Ref. 2).