Diffusion and Osmosis

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Objective Diffusion is the process that occurs when a certain concentrated volume of material moves to a less concentrated state. Osmosis is the movement of a solvent (as water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane. Terms for water flow are hypertonic (has low water concentration and high salt concentration than cells), Hypotonic (solution that has high water concentration and low salt concentration than cells), and isotonic (solution that has the same water and salt concentration as the cells). In this lab, we examined the water flow across the selectively permeable membrane of potato cells. We measured the net movement of the potato membrane by comparing the weight of a potato cube before and after incubation in 7%, 14%, 21%, 28%, and distilled water. Hypothesis: Alternative: The potato cells will undergo some kind of water movement after the solution. Null: The potato cells will not have a net movement, and osmosis does not have an effect on the cube. Materials and Methods: The materials used in this lab were five small beakers, distilled water, 7%, 14%, 21%, 28% of NaCl solutions, potato cubes, and paper. First, fill one of the beakers about one-third full with distilled water, and fill the others will all four solutions. There should be enough to cover the potato cubes. Mark the beakers so that you can identify the solution it contains. Peel potato and cut two cubes about 1cm by 1cm by 1cm. Then, gently roll each potato piece on a paper towel to remove the surface water. Using a balance boat, record its weight, and quickly immerse the piece in one of the experimental solutions. Repeat this procedure with the other potato piece, making sure that the balance boat is wiped dry between each weighing. Remove

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