The purpose of this lab was to see firsthand the diffusion of a substance across a selectively permeable membrane. Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration until both concentrations are equal, or as you could more professionally call it, equilibrium. This concept is one that we have been studying in depth currently in Biology class.
We separated into groups of two each, making sure that we had the following materials for the lab: graduated cylinder, plastic sandwich bag, starch solution, twist tie, 500-mL beaker, iodine solution, and a pair of goggles and an apron (for the person handling the iodine solution). Next we would put the starch
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Limitations As with all labs, there will be limitations that can come into play. We had one very good example of this in our class. Since there was not enough of the iodine already in stock for our project, Mr. Longfellow had to get some more if he wanted everyone to be able to do this project with comfort. So he went to several stores, finally deciding on one that he thought was not decolorized (because he did not know whether the decolorized iodine would have the reaction that normal iodine did). But as the writing for decolorized was small and out of the way, he did not know that he had, in fact, picked up a bottle of decolorized iodine still! And so, as he was unsure of, the reaction present in the examples using regular iodine were not present in the ones using decolorized iodine, leading to the assumption that the reaction has something to do with the agent in iodine that colors it. The other obvious limitation is the basic limitation in most anything that we do: human error. This basic factor that must be included because it could have affected most anything, even if a slight mistake didn’t entirely corrupt the entire lab. Examples of this are that the starch solution could have too little or too much starch, too little or too much water in it. There could be too little or too much iodine.