2. Make sure the water is at the same temperature – this ensures a fair test. Write down the temperature.
3. Use an electronic balance to weigh out 10 g of copper sulfate on a clock glass. 4. Add a small amount of this copper sulfate to the first test tube of water and shake gently.
5. Keep adding small amounts of copper sulfate until no more will dissolve in the test tube (you will see small particles at the bottom that do not dissolve).
6. Weigh the copper sulfate that remains on the clock glass and calculate how much has been used.
7. Repeat steps 3–6 using each of the other chemicals.
Temperature and solubility We know that all matter is made from atoms and molecules. When a solid (the solute) dissolves in a liquid (the solvent), the atoms and molecules of the solute are able to fit into the gaps around the molecules of the solvent. When all the gaps are full then no more solute can dissolve. This is then called a saturated solution. When a solvent is heated the atoms and molecules have more energy and can move more. What effect might this have on the amount of solute that can be dissolved?
SL
Extended Investigation How does temperature affect solubility? Design and conduct an investigation, using at least two different solutes, to find out if the temperature of a solvent affects the amount of solute that can dissolve. Compare your results with another group. Do you notice the same pattern in your results?
Crystals If a hot, saturated solution of copper sulfate (or another substance such as sodium chloride or alum) is allowed to cool slowly, crystals will start to form. This happens because as the solution
