How to make a supersaturated solution:
Rock Candy is made from a supersaturated solution of sugar water. Sugar is dissolved in a big kettle of water until no more sugar dissolves at room temperature. Then, the saturated solution is heated up. The higher temperature allows for more sugar to be dissolved, so more sugar is put in. As more and more sugar is put into the kettle, it dissolves, which makes the solution saturated at the new higher temperature. Now, if the sugar is cooled down very slowly, and no more sugar is added, the sugar will stay dissolved. As the temperature cools, the sugar dissolved at that higher temperature stays dissolved, and a supersaturated solution is made. At this lower temperature, the solution is unstable, and by putting a small crystal of solid sugar in the kettle, the extra sugar that is dissolved will attach itself to the sugar, and grow crystals, or rock candy.
Effects on Solubility
Solubility can be affected by the temperature of the solvent.
The graph at right shows the solubility of several solids at different temperatures. Any point on the curve is saturated. Therefore a saturated solution of KNO3 at 25 OC would contain approximately 40 grams of dissolved potassium nitrate.
Any point below the curve indicates an unsaturated solution. At 25 OC, an unsaturated solution of KNO3 would contain less than 40 grams of dissolved potassium nitrate.
|Diagram Courtesy of ChemCom 4th Edition|
Complete the following worksheet: Solubility and Concentrations
Links to more information/examples on Saturation and Solubility