Osmosis And Diffusion Lab Report

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Introduction Cells like to have some control over what gets in and what goes back out. This is called selective permeability (Tamarkin 2011). Two ways small particles can get past the cell membrane are through diffusion and osmosis (Tamarkin 2011).The terms diffusion and osmosis refer to the way small particles move. They are both examples of passive transport (Tamarkin 2011). Diffused particles move in a concentration gradient (Tamarkin 2011), which means they both move from areas of high concentration to areas of lower concentration. Imagine you have a cup of water and you just put a bit of food coloring in it, it does not just stay there. If you wait and do not stir the color in, it will eventually spread until it has distibuted evenly.…show more content…
Two dialysis bags were put into two different beakers of IKI (Iodine Potassium Iodide or Lugol's solution). One had salt added to it and one did not. This was to measure diffusion. Also, six different beakers were filled with tap water and inside each beaker was a dialysis bag, each with a different concentration of sucrose. This was to measure osmosis. It was hypothesized that the IKI/salt solution would diffuse into the dialysis bag with starch in it. This is because the IKI solutions are mixed into water. The water will make the salt (NaCl) dissociate into ions(Na+ and Cl-), making the contents in the outside have more particles than the starch (Diffusion, Osmosis,... 2003). Which, again, means that the IKI/salt solution will move into the dialysis bag because the contents of the bag have more particles. The other beaker with the IKI solution in it will not diffuse into the bag since the contents inside and outside have equal amounts of…show more content…
Some of the bags just gained more mass in proportion to their original masses. Not all of the bags weighed the same to begin with, so the change in mass (%) was calculated. Some error was expected, so the class shared data to get a more accurate calculation. The bags with the higher concentrations had a greater change in their mass. This is due to the osmotic gradient. Inside of the dialysis bags were a lot more particles than in the water. This made the solution on the inside hypertonic and the solution on the outside hypototic. Since the osmotic gradient always goes from hypotonic to hypertonic, the bags got heavier because there was more water inside of them. If the bags we tied without much room to spare, the bag could have exploded due to too much osmotic pressure (Tamarkin 2011). It made sense that solution in the bag with the highest concentration of sucrose would also have the highest change in mass (%) and the solution in the bag with the lowest concentration would have the lowest change in mass (%). This is again, because of the osmotic gradient. Since there is a lot more sucrose in the solutions with the higher concentrations, more water has to be moved to help make the solutions isotonic to each other. In the lower concentrations, not much osmosis has to happen to reach

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