University of Virginia
Physics Department

## More on Temperature and Solubility

A Physical Science Activity

### Student Activity

Materials

 Sodium chloride (10g) Graduated cylinder Potassium nitrate (10g) Hot plate 2 Test tubes (20 x 150 mm) 2- #2 solid stoppers Test tube rack Stirring rod 2 Beakers (250 mL) Safety glasses

Procedure

1. Place 10 mL of water into each of the two test tubes.
2. Add 10.0 grams of sodium chloride to one and 10.0 grams of potassium nitrate to the other.
3. Place both test tubes in a large beaker of water and stir the solutions with the stirring rod until both have completely dissolved.
4. Heat the solutions on the hot plate and stir continuously until the water in the beaker is boiling.
5. While heating, try to observe if the solubilities of the solids are changing equally as the temperature increases.
6. When the water has boiled, remove both test tubes and place each into a beaker of cold water and observe the changes taking place in each test tube.

Data Sheet

 While the water in the beaker was heating, did both the solids in the test tubes dissolve at the same rate or at different rates?     Describe what happened when the two test tubes were placed in the beaker of cold water.     If 5 grams of potassium nitrate (KNO3) were dissolved in 10 mL of water at room temperature, how much could be dissolved in 100 grams of water at the same temperature?     Solubility depends on three factors: the nature of the solvent, the nature of the solute and the temperature of the solution. Which factor was the variable in this experiment?