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Investigating the concentration of cell sap in potatoes

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Investigating the concentration of cell sap in potatoes Plan Osmosis is the movement of liquid through a semi permeable surface. The liquid passes from the dilute solution to the concentrated solution until both solutions are equal. This is needed for plants for them to get water from their roots to their stem and leaves. The cell wall of a plant cell is semi permeable. The sap inside a cell is slightly sugary. Only water molecules can pass through the membrane of the cell because they are small enough. Sugar molecules are too large to go through so they stay where they are, no matter how concentrated the solution may be. When placed in distilled water, osmosis will try and even out the concentration by absorbing in from the distilled water. This diagram explains what happens in this situation: Osmosis also works the other way round. When the cell is placed in a high concentration of sugar, the water from the sap vacuole flows out from the cell into the surrounding water until it is the same concentration. ...read more.


Variables This table shows all the variables I will be changing, keeping the same and measuring: Keeping Changing Measuring * The amount of water poured over the potato. * Starting weights * The concentration of the water. * The group weights of the potatoes * The start and end weights of the potatoes in each experiment. Prediction What I predict is that, the potato in the distilled water will gain in weight a lot. And the potato in the strongest solution will lose a lot of weight. I predict this because of what I have said in my introduction. The distilled water has a low concentration so more will be absorbed into the cell to even it out. And the potato in the high concentration will lose weight as water will be lost from inside the cell to even out the concentration. This is my predicted graph: Obtaining Results The tests were carried out as stated above and these were the results that were recorded: Concentration BEFORE AFTER BEFORE AFTER BEFORE AFTER Avg. ...read more.


My results conclude that in dilute water, the weight increases and in concentrated water, the weight of the potato decreases. Evaluating The experiment went quite well. We did have two weird weights of some potato so we did those again and got some more reliable answers. On the graph, the weights were all close to the line of best fit, except for the 0.1 molar one, we probably had some inaccurate answers or the solution we were using wasn't exactly 0.1 molar. My results did allow me to make a firm conclusion so therefore must be very reliable. To make this test error-free, then the potatoes would have to be all the same weight and all have the same surface area. Also, the concentration we use would have to be exactly correct and use only 5ml. The Petri dishes could also be held in an incubator to keep the same temperature. Another experiment to measure osmosis would be to place plants into different concentrations of sugar and water and test their leaves for any changes. This would show how far osmosis can go up the stem through different concentrations. ...read more.

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