An indicator is a substance that changes color when in the presence of the substance it indicates. In this experiment, IKI will be used an indicator to test for the presence of starch and glucose.
Materials (5) 100 mL Beakers |
*Stopwatch *You Must Provide
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Procedure
Note: The color results of these controls determine the indicator reagent key. You must use these results to interpret the rest of your results.
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Figure 4:Step 9 reference. |
Table 3: Indicator Reagent Data |
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Indicator |
Starch Positive |
Starch Negative |
Glucose Positive |
Glucose Negative |
IKI Solution |
Dark Purple |
Black |
n/a |
n/a |
Glucose Test Strip |
n/a |
n/a |
Light Green |
Yellow |
Table 4: Diffusion of Starch and Glucose Over Time |
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Indicator |
Dialysis Bag After 1 Hour |
Beaker Water After 1 Hour |
IKI Solution |
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Glucose Test Strip |
Purple |
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Post-Lab Questions
1. Why is it necessary to have positive and negative controls in this experiment?
2. Draw a diagram of the experimental set-up. Use arrows to depict the movement of each substance in the dialysis bag and the beaker.
3. Which substance(s) crossed the dialysis membrane? Support your response with data-based evidence.
4. Which molecules remained inside of the dialysis bag?
5. Did all of the molecules diffuse out of the bag into the beaker? Why or why not?