Diffusion Lab
This experiment was to symbolize the cell membrane, and the nutrients cells need to stay healthy. The prediction that was most common was that the iodine would somehow come in contact with the starch. The baggie acts as a cell membrane/barrier that only leaves gaps big enough for the iodine to squeeze through. This is the same concept as cells. The cell has a cell membrane, that is permeable, so that the nutrients and proteins can go through, but the organelles of the cells don’t go out. Concentration is the amount of molecules in proportion to the volume. This movement of molecules is called diffusion. Osmosis is this exact same movement, except osmosis only happens with water molecules. An indicator, such as the iodine, means that when it comes in contact with the starch, the solution turns purple. Diluting a substance means to lower the concentration of it. There are three terms that go along with concentration: hypertonic, hypotonic, and isotonic. Hypertonic means more concentration, hypotonic means less concentration and isotonic means equal concentration.
After placing the cornstarch–filled baggie in the iodine solution, it was left to sit there for a few minutes. When the baggie was taken out, the indicator (iodine) had left strips of purple in the cornstarch. Given more time, it would have turned all the contents of the bag purple. The main question with this result was: How did the iodine get into the bag? It’s quite possible. The bag acts as a selectively permeable membrane, which means that it is picky in what the membrane lets in. Since the iodine molecules were small enough to enter the bag, they were let in. They went in because they were diffusing, moving from an area of higher concentration to an area of lower concentration. On the other hand, even though the cornstarch wanted to diffuse, it couldn’t because the molecules were too big to pass through the barrier. This experiment was a replica of the cell system in human bodies, the iodine being the nutrients and energy the cell needs, and the baggie being the cell itself. By having this access to the cell, the nutrients can easily supply the cells, and the waste product can leave the cell, without any organelles sneaking out.
There are many connections that can be made to real life. First, an example of diffusion: when the stove in a kitchen is turned on, the gas used to fuel the fire diffuses into the air so it can be smelled. Another example of diffusion is a nail polish bottle. If it’s opened, the molecules diffuse and, again, it can be smelled from a distance. The third example of diffusion is when a fire is lit, you can easily smell the smoke from it, which means the molecules are diffusing. Last, but not least, if a cologne bottle is opened, the smell is overpowering, which is how you can tell it is diffusing!
