Semi-Permeable Membrane Lab
Your job?
DESIGN a lab with your lab group that demonstrates
diffusion.
With what, you ask?
A dialysis tube (semi-permeable) and a solution that
contains sugar and starch.
How will you know if you have succeeded?
Your procedure will allow you to prove which
molecule is larger: sugar or starch.
The following is a list of materials that you may use:
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Dialysis tubing (acts like a cell membrane)
String
Scissors
Sugar/starch solution (this contains sugar molecules,
starch molecules, and water molecules)
Beaker
Distilled water (100% water molecules)
Iodine
Benedict’s Solution (Hmmm, what do we use
Benedict’s for again??? Seems familiar…)
Dropper
Test tube
Test tube holder
Test tuber rack
Hot plate
Write your procedure in step form. Do not leave out any
details.
Answer the following questions in your notebook:
1. When the experiment was finished, what color was
the liquid in the tubing?
2. Did the starch molecules pass through the membrane
into the beaker? Explain how you figured this out.
3. Explain what happened to the iodine molecules.
4. Did the sugar (glucose) molecules pass through the
membrane into the beaker? How did you know?
5. According to your results, how does the size of the
starch molecules compare with the size of the sugar
molecules? How does the size of the starch molecules
compare with the iodine molecules?
6. A cell membrane is called semi-permeable and so is
the membrane of the bag you used in this lab. In
your own words, explain what semi-permeable means.
7. CONCLUSION: Thoughtfully explain exactly what
caused all of the results you got with your experiment.
(This should take you a minimum of 4 short
sentences.) Hmmm., if KJ is quickly grading this lab,
which question do you suppose she’ll look at most
closely??? Hmmm…