SBI4U
Factors Affecting the Rate of Osmosis
From: Biology 11 College Preparation (Nelson 2003)
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.
Question
How do changes in solute concentration and temperature affect the rate of osmosis?
Prediction
Predict how solute concentration and temperature affect the rate of osmosis.
Materials
safety goggles
5 pieces of dialysis tubing, each about 15 cm long
distilled water
paper towel
40% sucrose stock solution
transfer pipettes
5 250-ml beakers
masking tape for labels
10mL graduated cylinder
funnel
electronic scale
*Wear eye protection throughout this activity*
Procedure
Part 1: 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:
5% sucrose
10% sucrose
20% sucrose
Keep 10 mL of the 40% sucrose solution.
4. Rub the dialysis tubing between your fingers to find and 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.
Part 2: The Effect of Temperature on the Rate of Osmosis
Experimental Design
1. 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. Have your teacher
approve your list of materials and procedure, then carry out your experiment. Record your results in
a suitable chart, and draw suitable graphs of your results.
Analysis
a.
b.
c.
d.
Analyze your graphs for patterns and answer the Question.
Did all dialysis tubes increase in mass? If not, explain.
Which dialysis tubes had the greatest increase in mass in Part 1? Why?
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
e. Evaluate your predictions for Part 1 of the investigation.
f. Describe any sources of error in Part 1 of the investigation.
g. Suggest possible improvements to the procedure in Part 1.