Osmosis Lab
Problem: Use the process of osmosis to determine which of three molecules (water,
starch, and iodine) can cross a selectively permeable membrane called dialysis tubing.
Research: Tell what you know about the process of osmosis and isotonic, hypotonic, and
hypertonic solutions. What do you know about the three molecules involved? How do
you know this information?
Hypothesis: Based on what you know about the molecules, solutions, and osmosis,
briefly explain what you think will happen.
Experimental Materials:
2 250 mL (or larger) beakers
Starch solution
Iodine
Dialysis tubing
String
Water
Eyedropper
Graduated Cylinder
Scale Balance
Experimental Procedure:
1.
2.
3.
4.
Clean and dry glassware.
Open moist dialysis tubing by rubbing between thumb and finger.
Tie off one end of the tubing with string.
Carefully pour starch solution into one of the tubes and water into the other.
Leave room to tie off the other end of the tube to form assort sausage-shape. Each
“sausage” should not be too full. Allow room for liquid to enter if the need arises
due to osmosis.
5. Determine the mass of each liquid filled tube using a balance. Be sure to record
your initial measurement, and the time the measurement was made.
6. Put each liquid filled tube into a 250 mL beaker and fill with enough water to
cover the tubing.
7. Put a few mL of starch solution into a test tube and add a few drops of iodine.
Record your observations. Dispose of the solution, rinse, dry and return the test
tube to its box.
8. About ten minutes before the end of class remove each little “sausage” from its
beaker, pat it dry with a paper towel, and measure its mass. Record the time and
the mass.
9. Return each tube to its beaker, and add a dropper full of iodine to the water in
each beaker, and store the beakers in a safe place overnight.
10. Upon returning to class, make a visual inspection of your beakers and record your
observations.
11. Remove each tube from its beaker, pat dry, and determine the mass. Record your
findings, making not of the time and date.
12. Dispose of the tubes in the trash (it is all biodegradable), but put the liquids down
the sink. Rinse, dry and return glassware to its proper place.
Data:
1.
2.
3.
4.
Draw the beginning set-up. Label your model.
Make a table and record all your mass measurements.
Write out your visual observations.
Draw the model of the final results. Label your drawing.
Conclusion:
Write an analysis AT LEAST THREE PARAGRAPHS IN LENGTH that
indicates whether your hypothesis is correct or incorrect. Also, define and discuss the
process of osmosis and why it is important in living system. Explain the type of solutions
you created (iso-, hypo-, hypertonic) and tell what data shows that these are the solutions
you created. Be sure to utilize your findings in this lab to support your statements, or be
able to defend your findings if they do not coincide with the basic concept of osmosis
transport. Feel free to give examples of osmosis and diffusion at the work in living
things.
Questions:
1. In this lab, what did the following things represent: dialysis tubing, water in
beaker, starch, the “sausage”, iodine?
2. Did the mass for each tube change?
3. What would cause the mass to increase? To decrease? To remain the same?
4. What type of solution (hypertonic, isotonic, and hypotonic) would cause the mass
to increase, decrease, or stay the same?
5. Draw a model that illustrates what happened in each of your beakers if you didn’t
draw it in the data selection.