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Double Science Coursework - Osmosis

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Introduction

Double Science Coursework Plan Aim : The aim of this investigation is to identify any pattern that may exist in the way water moves in and out of plant cells. Variables: Dependant Variables : Mass of potato pieces Independent variables: Concentration Of Solutions Controlled Variables: Solution Volume Surface Area Duration Of Experiment Temperature Weighing scales. Background Research: Plasmolysis: This is the contraction of cells within plants due to water loss through the process of osmosis. This happens when there is a higher concentration of water inside the cell than outside the cell, and thus water is drawn through the selective membrane from the area of high water concentration to the area with low water concentration. Hypotonic Solution: This is a solution with a lower concentration of solute, and thus a higher concentration of water than the cytoplasm of the cell. Therefore water moves into the cell, causing the cell to swell up. Hypertonic Solution: This is a solution with a higher concentration of solute, and thus a lower concentration of water than that within the cytoplasm of the cell. Therefore water moves out of the cell, causing it to contract. Isotonic Solution: This is a solution which has the same concentration of solute as that within the cell. ...read more.

Middle

* Then using a ruler and a scalpel, we cut the pieces to the same length so as to ensure the same surface area. * We then placed the pieces in weighing boats and measured their mass on weighing scales. * Next we prepared the solutions by inserting the right amount of solute into 100cm� of distilled water in a measuring cylinder. * We then stirred it using a stirring rod in a beaker. * After that we measured out 25cm�of the solutions using a measuring cylinder. * Then we poured 25cm� of the solutions into the test tubes. * Next we placed the potato pieces in the test tubes containing the solutions. * We placed the test tubes in holders, and left them for 6 hours. * Then we extracted the potato pieces, dried them and measured their mass. * Lastly, we recorded the results on a table, and calculated the average mass change for each concentration. Reliability: * We used the same weighing scale for all measurements so as to ensure that there was no discrepancy in the recordings. * We used the same core borer to make sure that the pieces had the same circumference. * We properly dried the potato pieces to ensure that any water on the surface of the potatoes would not affect the results. ...read more.

Conclusion

The mass of the potatoes did decrease for the higher concentrations, where water left the cell due to the concentration of water being higher inside the cell. Evaluation I believe that my results are fairly reliable, as I have done them to the best of my ability with the equipment available to me, controlled the variables carefully, and double checked all measurements and also made sure that the apparatus was properly set up every time. Through my graph, I could identify two results that might possibly be anomalous, as it did not completely conform with my line of best fit. The results for 1.6% showed a mass decrease of 0.0466 g, when it should've been around 0.09g, and the results for 0.8% showed a mass increase of 0.0566g, when it should've been around 0.03g I believe that this could have come about due to us not drying the beaker and the test tubes properly, and thus causing the solution to become more diluted, meaning that the diffusion gradient would be decreased, and less water would be lost by the plant. Therefore, if I were to repeat the experiment, I would take greater care in drying the apparatus, or maybe even use fresh beakers and test tubes for each test. ?? ?? ?? ?? SG 11A Cand No. - X Centre No. - X ...read more.

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