Corn.Starch.Iodine.Lab.pdf
Cornstarch & Iodine LabName: Period: Problem: Do all sized particles move across membranes during diffusion?Background Information:Iodine indicates the presence of starch. Specifically, iodine turns cornstarch purple.Dialysis tubing is called semi-permeable which means it has many microscopic openings that allow small amounts of air or water to enter and leave. Larger things cannot pass through these openings.Diffusion is the movement of molecules from a high concentration to a low concentration.Materials:Dialysis tubing? BeakerIodine? corn starchEye dropper? spoonProcedure:Fill the 1000mL beaker halfway with water.Put 10 drops of iodine into the water and swirl.Using the spoon, put a teaspoon of cornstarch into the small beaker. Add water to the small beaker, about 100mL, stir well.Get one piece of dialysis tubing and tie a knot in one end. Using the small graduated cylinder place 15-20mL of the cornstarch water into the dialysis tubing. Tie a knot in the other end. Place the bag into the water with the iodine and let it sit for 15 minutes.While you wait answer the questions below:Data/Observations:Molecules tend to move from areas ofconcentration to areas of concentration.Which is more concentrated in starch, the dialysis tubing or beaker? Which is more concentrated in iodine, the dialysis tubing or beaker? If the dialysis tubing was permeable to starch, which way would the starch move, into the bag or out of the bag? If the dialysis tubing was permeable to iodine, which way would the iodine move, into or out of the bag? If the dialysis tubing was permeable to iodine, what color would you expect the liquid in the dialysis tubing to turn? What about the liquid in the beaker? ________________If the dialysis tubing was permeable to starch, what color would you expect the liquid in the dialysis tubing to turn? What about the liquid in the beaker? 106680052070000Make a prediction about what you think will happen:1066800-24066500Data Table:Starting ColorColor after 15 minutesSolution in dialysis tubingSolution in BeakerConclusions: (Use lined paper if you need more space)*Based on your observations, which substance moved, the iodine or thestarch? How did you determine this? 1066800-3746500499681524130000The dialysis tubing was permeable to which substance?419671520066000Is the dialysis tubing selectively permeable?Sketch the cup and baggie in the space below. Use arrows to illustrate how diffusion occurred in this lab. Be sure to label the parts of your diagram.10668001038860001066800131826000What would happen if you did an experiment in which the iodine solution was placed in the dialysis tubing, and the starch solution was in the beaker? Be detailed in your description.1066800-3168650010668005207000010668008001000010668001079500001066800135890000Plastic bags are also selectively permeable, why do you think it is not a good idea to store iodine in a plastic bag based on that information? ................
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