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Osmosis
Equipment : Vinegar (5% Acetic Acid), large eggs, beakers, potatoes, saturated salt water, raisins, white corn syrup.


Procedures : NOTE: All of these demonstrations will require at least 24 to 48 hours advanced preparation.

Dissolve the shell off of several eggs with the vinegar. This will take at least 12 hours. Compare the naked egg to a regular egg with a shell and notice the dramatic increase in size. This increase is due to absorption of water through the permeable membrane. Take one of the naked eggs and place into a beaker of corn syrup and let stand overnight. The egg will lose water to the corn syrup and will come out looking much like a large raisin.

Prepare two beakers, one with salt water and one with plain water. Cut some 1/4" slices from a potato and drop into each beaker. Wait 20 to 30 minutes. Pull the slice out of the plain water and observe that it does not bend easily and will in fact break crisply. Do the same to the slice in the salt water and observe that is bends quite readily and is very hard to break. This is due to the movement of water from the potato cells to the salt water.

Place the raisins in a beaker of plain water and let stand overnight. Compare regular raisins to the soap raisins.

The Effect of Osmosis on Raisins
Purpose: To observe and measure the effect of osmosis on raisins.
Materials: 5 raisins, thread, rulers, beaker, water, and paper towels.
Procedure:
1. Obtain 5 raisins.
2. To measure the circumference of the middle of each raisin, wrap a piece of thread around the fattest part of the raisin and measure the length of the wrapped portion of thread against a ruler. Measure in cm.
3. Calculate the average.
4. Place the raisins in a beaker or cup and fill the cup 3/4 full with water to cover the raisins.
5. After 2 days, pour out the water and dry the raisins. Measure the raisins again following
step 2. Calculate the average for the "puffy" raisins.
Results:
Before..........................After
1. ................................ 1. ................................
2. ................................ 2. ................................
3. ................................ 3. ................................
4. ................................ 4. ................................
5. ................................ 5. ................................
Questions:
1. What was the average difference (in cm) between your raisins before and after?

2. Define and explain the process that made the raisins "puffy."