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The aim of the investigation is to find the exact concentration of the cell sap of a potato. What is osmosis?Osmosis is the movement of water across a semi permeable membrane from a highly water concentrated

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Osmosis coursework The Aim The aim of the investigation is to find the exact concentration of the cell sap of a potato. What is osmosis? Osmosis is the movement of water across a semi permeable membrane from a highly water concentrated region to a low water concentrated region. Water potentials High water potential is a medium that is mostly all water with very little solute whereas a solution with a low water potential has got lots of dissolved in its solution and little water content. Equipment I will need Borer Accurate scales Distilled water White tile Forceps Glucose solution (C6 H12 O6) Measuring cylinder Ruler Scalpel Scales Method * Cut a cylindrical chunk of potato out using the borer to 2cm/3cm * Weigh it. * Put the potato into the tube with solution * Leave over night * Re weight and work out the change Preliminary work Distilled Water In 1M Glucose solution Before 0.95 0.93 After 1.07 0.68 As you can see in distilled water the potato gained mass showing that it has taken on water and that cell sap must have a lower concentration of water then the distilled water, this causes the cells to swell. In the glucose solution the Osmosis occurs in the opposite way to that of the distilled water the water travelled out of the potato and into the glucose solution until equilibrium occurs. ...read more.


I will also do the experiment twice and I will use an average for my graph. I want to get the most accurate results because this will give me a better result and by being accurate there will not be as many mistakes. Prediction My own Prediction is that when the potato is in the water solution will take on more water this is shown in my preliminary work and this is because there is a higher water potential in the water so the water will be taken across into the potato by osmosis. This also means that the Potato will lose weight in the glucose solution as the water in the potato will move across the membrane into the glucose solution as there is a lower water potential there. I also believe the answer will be closer to 0M then 1M because in my preliminary work there was a smaller percentage change on the distilled water then the 1m solution. I also think my results will give me a straight line graph as they are directly proportional until the potato cant take on any more which is when we use distilled water. Results Experiment Concentration of solution Mass before Mass after Mass change Mass Change x100 Mass before 1 0.0M 0.91g 1.00g 0.09g 9.89% 0.2M 0.94g 0.95g 0.01g 1.06% 0.4M 0.93g 0.80g -0.13g ...read more.


Evaluating I feel my results are pretty accurate they all fit very close to the line of best fit there are only very small variations. The method I used was a simple step method that gave me the results I needed and wasn't very complicated. I feel that the results are strong enough to support the conclusion I have written. They follow a strong positive correlation and nearly all of the mass changes are within 5 grams of each other, and they are nearly all within 5 % of each other on the percentage change column, which is accurate enough to support my initial prediction. There was one anomaly in my results in the 0.4M solution where both the mass and percentage change is more than 5g and % this could have been caused by a different size chunk of potato. I could of repeated the experiment more times to get a better average and that would be able to help get rid of any anomalies also to of improved the experiment or if I was to do it again I could of used a more accurate weighing scale or a sharper scalpel as the one I used was quite blunt and made it hard to cut exactly the right size. Taking it further If I was to take this experiment further I could look at different initial masses, surface areas or different varieties of potatoes. By Naomi Colcomb ...read more.

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