Osmosis
      
Urbanek, Robert A.                    Corliss High School
                                      821-2515
                          

Objectives:

To teach concepts of chemical and physical changes, and the 
difference between osmosis and diffusion in the movement of
molecules in a liquid environment.

Apparatus needed:

1. Thistle tube
2. Five 250 mL beakers
3. Three l00 mL beakers
4. Six feet or more of dialysis tape 
5. 1000 mL of starch solution
6. Iodine solution with eye dropper
7. 200 mL of 1% salt solution 
8. 200 mL of 2% salt solution
9. Three 100 mL Erlenmeyer flasks
10. 1 L bottle of distilled water
11. 2 peeled raw potatoes
l2. 500 mL of .1 M  Copper Sulfate solution
13. Four graduated cylinders
14. One fresh carrot
15. 40-50 cm of glass tubing
l6. 5 mL of sugar syrup

Recommended Strategy

1. Soften three pieces of dialysis tubing by holding them under 
   running water and rubbing the ends between two fingers until
   the tubing separates.
2. Prepare three bags by tying a knot in one end of each
   piece of tubing approximately 15 cm long.
3. Carefully measure 20 mL of 1% salt solution and add it to one bag.
4. Tie a name tag to the other end of the bag and place this bag 
   upright in 250 mL beaker.  Fill the beaker half full of the 10%
   salt solution.
5. Measure 20 mL of 10% salt solution and place it in another 
   dialysis bag.  
6. Place this bag upright in another 250 mL beaker and add 1% salt
   solution to this beaker until the liquid is the same as that in the
   first beaker. Set both aside for about 15 minutes.
7. Add 25-30 mL of starch solution to the third dialysis bag. 
   Remember to rinse the third dialysis bag on the outside first.
8. Place the bag upright in another 250 mL. beaker. Fill the
   beaker two-thirds (2/3) full with water. Add 3 or 4 drops 
   of Iodine solution into the beaker.  Observe the bag after 15 
   minutes or the next day.  What is the color of the starch solution 
   in the bag? 
9. After the allotted time, compare the levels in the first two
   beakers containing the salt solutions.  Has one decreased?
   Has the other increased?
10.Take the carrot and core out of the cortex about half way from the 
   wide top.  Fill the hole with sugar syrup, and carefully put the 
   glass tubing all the way into the syrup and the hole. 
11.Place the carrot upright in a beaker of water so that the top of 
   the carrot is above the water level.  Mark the level of syrup in
   the glass tube, then put aside and record this level every 24 
   hours.  Did the syrup go up or down?