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|
10 mL 1% Glucose Solution, C6H12O6
4 Glucose Test Strips
(1) 100 mL Graduated Cylinder
4 mL 1% Iodine-Potassium Iodide, IKI
5 mL Liquid Starch, C6H10O5
4 Rubber Bands (Small; contain latex, handle with gloves on if allergic)
*15.0 cm Dialysis Tubing
*You Must Provide
|Attention!Do not allow the open end of the dialysis tubing to fall into the beaker. If it does, remove the tube and rinse thoroughly with water before refilling with a starch/glucose solution and replacing it in the beaker.||Note:Dialysis tubing can be rinsed and used again if you make a mistake. Dialysis tubing must be soaked in water before you will be able to open it up to create the dialysis “bag”. Follow the directions for the experiment, beginning with soaking the tubing in a beaker of water. Then, place the dialysis tubing between your thumb and forefinger and rub the two digits together in a shearing manner. This should open up the “tube” so you can fill it with the different solutions.|
Note: The color results of these controls determine the indicator reagent key. You must use these results to interpret the rest of your results.
|Figure 4:Step 9 reference.|
|Table 3: Indicator Reagent Data|
|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|
|Indicator||Dialysis Bag After 1 Hour||Beaker Water After 1 Hour|
|Glucose Test Strip||Purple|
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?
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