A. PROBLEM/RESEARCH QUESTION
1. How does increasing molarity of sucrose affect osmosis through dialysis tubing?
1. The independent variable in this lab is the molarity of sucrose each dialysis bag is filled with. The time (30 minutes), the temperature (23C) and the type of dialysis tubing used are all constants. 2. The dependent variable is the final mass of the dialysis bag. 3. The control in the experiment is distilled water, as it does not contain sucrose solution.
C. MATERIALS NEEDED
4. Five 30 cm strips of dialysis tubing
5. Five clear plastic cups
6. 10 pieces of yarn
7. Distilled water
8. Sucrose solutions (with molarities of: 0.2, 0.4, 0.6, and 0.8) 9. Calculator
10. Electrical balance
14. Graduate cylinder
1. Obtain five 30 cm strips of presoaked dialysis tubing. 2. Tie a knot in one end of each piece of dialysis tubing with a small piece of yarn to form 5 bags. 3. Pour 20 mL of each of the following solutions into separate bags: A. Distilled water
B. 0.2 M sucrose
C. 0.4 M sucrose
D. 0.6 M sucrose
E. 0.8 M sucrose
4. Remove air from each bag by drawing the dialysis bag between two fingers. Tie off the other end of the bag. Make sure to leave sufficient space for expansion of the contents in the bag. 5. Rinse each bag gently with tap water to remove any sucrose solution spilled during the filling. 6. Carefully blot the outside of each bag, find and record the initial mass of each bag. 7. Place each bag in an empty cup, and label the cup to indicate the molarity of the solution in the dialysis bag. 8. Fill each cup with distilled water. Be sure to completely submerge each bag. 9. Let cups of water with dialysis bags in them stand for 30 minutes. 10. At the end of 30 minutes, remove the bags from the water. 11. Carefully blot the outside of each bag, find and record the final mass of each bag. 12. Record, process, and present data.
II. DATA COLLECTION AND PROCESSING
E. The raw data is compiled in order of increasing molarities in the first column. The initial mass and the mass after 30 minutes has been recorded in order to determine the effect of increasing molarity on mass.
Mass of dialysis tubing bags before and after 30 minutes of submersion in water during which osmosis took place | Contents of Bag| Initial Mass (g) + 0.100 g| Mass after 30 minutes (g) + 0.100 g| Difference in mass of bags (g) + 0.100 g[Mass after 30 minutes – Initial Mass]| Distilled Water (0.000M)| 21.70| 22.20| 0.500|
0.200 M sucrose| 22.88| 24.60| 1.800|
0.400 M sucrose| 23.15| 26.15| 3.000|
0.600 M sucrose| 23.20| 26.80| 3.600|
0.800 M sucrose| 22.53| 28.25| 5.720|
The fourth column in the table, the difference in the mass of the bags (mass after 30 minutes – initial mass) is included so that the trend of increase can easily be seen. This displays that as molarity of sucrose increases, the mass of the bags, or the contents of the bag increases/expands.
F. Calculating the percent change will further prove that an increasing molarity, yields in a larger mass after 30 minutes of undergoing osmosis.
Calculated percent change of mass in dialysis bags from initial mass to mass after 30 minutes| Contents of Bag| Percent change Formula [mass(g)] + 0.100 g:Mass after 30 minutes – Initial Mass X 100Initial Mass| Percent change in mass of contents of dialysis bags| Distilled Water (0.000 M sucrose)| 22.20 – 21.70 = 0.500 X 100 = 21.70 21.70| 2.30%| 0.200 M sucrose|...