This experiment uses some basic chemical terminology. Begin by explaining that a solute is the substance that is broken into smaller particles when dissolved in a solvent. A solvent is the substance that "holds" the solute (remember that water is the universal solvent). A solution that is saturated can hold no more solute and will not allow anything else to be dissolved. These definitions are all in the worksheet for the students (below).
Some students may not know how to read the measurements on the side of the beakers or flasks. It's probably a good idea to review this for them.
Does it make a difference which solvent is used? For example, can one solvent hold more solute than another can?
Have the students work in small groups. As a reminder, all the solvents in the first experiment should be at room temperature. One student can fill up a beaker with 200 ml. (50 ml. if you're short on time) of distilled water. Students should add sugar to the beaker and stir until the solution is saturated. Once the saturation point has been reached, another measurement should be taken and recorded. This process should be repeated with the tap water and the club soda. Have the students answer the first two questions on the worksheet.
What effect does temperature have on the saturation point?
Have the students take measurements on the temperature of room temperature water. Then have the students add sugar until the solution is saturated. (If you're short on time, have the students take the temperature in part one with the tap water since the results should be almost the same.) Repeat the process with cold water and then hot water. When completed, have the students answer question three on the worksheet.
Things to remember:
A.) Solute: the substance that is broken into smaller parts when dissolved
B.) Solvent: the substance that "holds" the solute.
C.) Saturated solution: will not allow anything else to be dissolved.
Solvent (water) Solute (sugar--tsp.) Volume before Volume after
Distilled water 200 ml.
Tap water 200 ml.
Club soda 200 ml.
Measure 1 cup of water for the next part of the experiment.
Temperature F C Solute (sugar--tsp.)
1. Which solvent can hold the most solute (distilled water, tap water, club soda)?
2. Did the volume change in the club soda? If so, why?
3. What effect does temperature have on the amount of solute (sugar) that can be held in solution (sugar dissolved in water)?
Shawn Len, 2000.