SBI4U
Name: _______________
Factors Affecting the Rate of Osmosis
In this investigation, you will determine how environmental factors such as solute concentration and
temperature affect the rate of osmosis through dialysis tubing. The investigation is divided into two
parts: Part 1 and Part 2. In Part 1, you will investigate the effect changes in solute concentration
have on the rate of osmosis. In Part 2, you will investigate the effect of changes in temperature. A
step-by-step procedure is provided for Part 1. You will design and carry out the procedure for Part 2.
Materials Needed:
safety goggles
distilled water
40% sucrose stock solution
5 250-ml beakers
10mL graduated cylinder
electronic scale
5 pieces of dialysis tubing, each about 15 cm long
paper towel
transfer pipettes
masking tape for labels
funnel
*Wear eye protection throughout this activity*
Procedure:
The Effect of Solute Concentration on the Rate of Osmosis
1. Soak the 5 strips of dialysis tubing in a beaker of tap water for approximately 2 minutes.
2. Using masking tape, label the 5 beakers as follows (one label per beaker):
0% sucrose
20% sucrose
5% sucrose
40% sucrose
10% sucrose
3. Using transfer pipettes, the graduated cylinder, and distilled water, dilute the sucrose stock
solution provided to produce 10 mL of the following three sucrose solutions:
How to mix solution:
10 mL of 5% sucrose solution
____ mL of 40% sucrose solution + ____ mL of distilled water
10 mL of 10% sucrose solution
____ mL of 40% sucrose solution + ____ mL of distilled water
10 mL of 20% sucrose solution
____ mL of 40% sucrose solution + ____ mL of distilled water
10 mL of 40% sucrose solution
10 mL of 40% sucrose solution
4. Rub the dialysis tubing between your fingers to find an opening. Tie a tight knot near one end of
the dialysis tubing. Repeat with the other pieces of tubing.
5. Using a graduated cylinder (and funnel, if necessary), pour 10 mL of the solutions you prepared in
step 3 into corresponding dialysis tubes. (Rinse the graduated cylinder with tap water and shake
dry between solutions.)
6. Fold over and twist the open end of each dialysis tube. Remove excess air from the tube, making
sure that it remains limp, then tie each end in a knot. Dry the outside of the tubes with paper
towel. Place each dialysis tube into the correspondingly labelled beaker.
7. Measure and record the mass of each dialysis tube.
8. Remove the dialysis tubes (being careful not to mix them up!) and fill each beaker with 200 mL of
distilled water at room temperature.
9. Place the corresponding dialysis tube into each beaker and wait 20 minutes.
10. After 20 minutes, remove the dialysis tubes, blot them dry, and measure and record their masses
(again, being careful not to mix them up!).
11. Use your recorded values to determine the percent mass change for each dialysis tube using the
following equation:
% mass change = (mafter - mbefore) ÷ mbefore x 100%
Record the % mass change for each dialysis tube in the chart.
12. Discard the solutions and dialysis tubes according to your teacher's instructions.
13. Draw suitable graphs of your results.
Reference:
This lab was taken from pages 65-66 in: Biology 11 College Preparation (2003)
Authors: Maurice Di Giuseppe, Douglas Fraser, Barry LeDrew, Jill Roberts
Publisher: Nelson (Thomson Canada Ltd.) in Toronto, Ontario
Answer the following questions. Include the answers to the Analysis & Evaluation questions in the
Discussion & Conclusion section of the lab report. The lab design (Extension question) should be
included as an Appendix in your lab report.
Analysis Questions:
a. Analyze your results for patterns. What can you conclude about how changes in solute
concentration affect the rate of osmosis?
b. Did all dialysis tubes increase in mass? If not, explain.
c. Which dialysis tubes had the greatest increase in mass in Part 1? Why?
d. Describe the five liquids in the dialysis tubes in Part 1 as hypotonic, hypertonic, or isotonic with
respect to the distilled water in the beakers.
Evaluation Questions:
e. What was your hypothesis on how changes in solute concentration would affect the rate of
osmosis? How accurate was your prediction?
f. Describe any sources of error in Part 1 of the investigation.
g. Suggest possible improvements to the procedure in Part 1.
Extension Question:
h. Design a procedure for determining the effect that a change in temperature has on the rate of
osmosis. Include as many controls as possible, and list safety precautions.