- University of Virginia
- Physics Department
Temperature and Solubility
A Physical Science Activity
2003 Virginia SOLs
- PS.5 (Due to the revised 2003 SOLs, this activity no longer
corresponds directly to PS.5, but still can be used to demonstrate physical
- understand that the solubility of a solute is dependent on the temperature
of the solvent;
- understand that the solubility of a substance in water is a characteristic
physical property only at a range of temperatures;
- use the following skills: observing, inferring, measuring, comparing and
- Does temperature effect the solubility of solutes?
The two solids used in this experiment are sodium chloride and
potassium nitrate. Both are white solids and have similar
solubilities at room temperature.
- Before students arrive in class mass out 10.0 grams of each
chemical on separate pieces of paper and place 10 mL of water in
two separate test tubes.
- When the students arrive in class, place the salt in one of
the test tubes and the potassium nitrate in the other. Stopper and
shake the test tubes until no more of each chemical will dissolve.
- Show the students that the two solids have slightly different
solubilities at room temperature. Ask the students if these
chemicals will dissolve similarly at different temperatures.
The solubility of a substance indicates how much of a substance
will dissolve in a given volume of water. The substance being
dissolved is the solute. The substance dissolving is called the
Solubility is a characteristic physical property of both the
solute and the solvent. It is usually expressed in complex units of
grams of solute per 100 mL of solvent. If the student knows the
solubility of a substance in a determined amount of solvent, he or
she can easily calculate the minimum amount of solute needed for the
amount of solvent being used. For example, if a solid powder has a
solubility of 10g/100 mL of water, then 1.0 grams of the same solid
would need 10 mL of water to dissolve. However, most chemicals change
their solubility with the temperature of the solvent and they do so
in a non-linear fashion. The true solubility of a solute in a
particular solvent must include its solubility at a range of
temperatures. Two chemicals may dissolve the same in water at one
temperature but very differently at another temperature.
To print out the Student Copy only,
- 2 Test tubes (20 x 150 mm)
- Place 10 mL of water into each of the two test tubes.
- Add 10.0 grams of sodium chloride to one and 10.0 grams of
potassium nitrate to the other.
- Place both test tubes in a large beaker of water and stir the
solutions with the stirring rod until both have completely
- Heat the solutions on the hot plate and stir continuously
until the water in the beaker is boiling.
- While heating, try to observe if the solubilities of the
solids are changing equally as the temperature increases.
- 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.
To print out the Data Sheet only,
- 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
An interested class can determine the solubility of potassium
nitrate at various temperatures by assigning each group of students a
different temperature for the water. The data from each group can be
collected and a solubility curve for potassium nitrate constructed.
Pass out a solubility graph of potassium nitrate and other common
chemicals. Have students answer questions concerning the solubilities
of the solids at different temperatures using the information on the