Design a way to determine the effects of different concentrations of starch on the mass of dialysis tubing bags when the bags are allowed to sit water for several hours. Plan to put different concentrations of starch solutions in the bags. You may want to use iodine as a visual indicator.
Write a lab protocol that includes and identifies the following criteria. You may list the steps in the procedure for your lab.
- Variable (dependent and independent)
- Replication
- Control
- Hypothesis (If/related to/then format you learned earlier)
- Data table
- Expected results and explanation for results
Title: Determining the Effects of Different Concentrations of Starch on the Mass of Dialysis Tubing Bags
Objective:
To investigate how different concentrations of starch solutions affect the mass of dialysis tubing bags when left in water for several hours, using iodine as a visual indicator.
Variables:
Dependent Variable: Mass of dialysis tubing bags
Independent Variable: Concentration of starch solution
Materials:
1. Dialysis tubing bags
2. Starch solutions of different concentrations (e.g., 0%, 1%, 5%, 10%, and 20%)
3. Distilled water
4. Iodine solution
5. Beakers
6. Weighing scale
7. Stopwatch
8. Pipettes
9. Marker or labels
10. Paper towels
Procedure:
1. Prepare the starch solutions of different concentrations by dissolving the appropriate amount of starch in distilled water. Label each beaker with the corresponding concentration.
2. Cut equal-sized strips of dialysis tubing from a roll and rinse them in water to remove any chemicals or impurities.
3. Measure and record the initial mass of each dialysis tubing strip.
4. Place one strip of dialysis tubing into each labeled beaker containing the respective starch solution. Ensure that the bags are fully submerged.
5. Start the stopwatch and let the bags sit in the solutions for a predetermined period (e.g., 6 hours).
6. After the specified time, carefully remove the bags from the solutions, ensuring not to spill any liquid.
7. Blot the bags gently with paper towels to remove excess moisture and prevent contamination.
8. Measure and record the final mass of each dialysis tubing strip.
9. Prepare a data table with the concentration of starch solutions, initial mass, final mass, and change in mass for each bag.
10. Calculate the change in mass for each bag by subtracting the initial mass from the final mass.
11. Rinse the dialysis tubing bags with water to remove any residual starch or iodine.
12. Repeat steps 3-11 for each concentration of starch solution, ensuring replication for reliable results.
13. Finally, analyze the data and draw conclusions based on the obtained results.
Control:
To establish a control group, include a dialysis tubing bag filled with distilled water instead of starch solution. This will allow for comparison and help identify any specific effects caused by starch solutions.
Hypothesis:
If the concentration of starch solution increases, then the mass loss of the dialysis tubing bags will also increase. This is because starch molecules are larger than water molecules, and as their concentration increases, the movement of water molecules out of the bag through osmosis will be hindered.
Data Table:
Concentration of Starch Solution | Initial Mass (g) | Final Mass (g) | Change in Mass (g)
------------------------------------------------------------------------------
0% |
1% |
5% |
10% |
20% |
Expected Results and Explanation:
With higher concentrations of starch solutions, it is expected that the dialysis tubing bags will experience a greater decrease in mass, indicating that water molecules are leaving the bag through osmosis. This is because the higher concentration of starch molecules creates a hypertonic environment, causing water to move from an area of lower solute concentration (inside the bag) to an area of higher solute concentration (the starch solution). The iodine solution can be used as a visual indicator to confirm the presence of starch in the bags and determine the extent of starch diffusion. The intensity of the blue color observed in the dialysis tubing bags after the experiment indicates the permeability of starch molecules across the membrane.