Osmosis Across a Membrane
Observe the movement of water across a semipermeable membrane.
Dialysis bags (4 per group)
15% sucrose solution
30% sucrose solution
Triple beam balance
Beakers (4 per bench)
- Stir rods
- Obtain 4 strips of dialysis tubing and tie a knot in one end of each using the dental floss.
Pour approximately 10ml of each solution into separate bags (see table below).
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|Tonicity of bag?|
Remove most of the air from the bag (but leave a little bit of space) and tie the bag.
Blot the bags to remove any sugar that may have spilled; check the bags for leaks.
Record the weight of each baggie in the data table.
Place a bag in each beaker (be sure to keep track of which bag is in which beaker!). Fill the beakers with enough of the appropriate solution to cover your bags (refer to the above table).
Predict what you think will happen during the experiment.
Record weight every 10 minutes in data table.
After 30 minutes, remove the bags from solution and record the final weight.
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|Weight at 0 min|
|Weight at 10 min|
|Weight at 20 min|
|Weight at 30 min|
1. Did you results match your predictions? Propose an explanation for why your results (either overall or an individual bag) may have differed from what you were expecting.
2. Based on what you have observed, are the dialysis bags permeable to sucrose?