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Osmosis Lab

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Introduction

Osmosis Lab Examination of how the concentration of salt in a solution outside of a semi permeable membrane affects the rate of Osmosis Sean Williams Lab Partner: Sean Clark IB Biology Standard Level September 30, 2010 Introduction Osmosis is the movement of water molecules from an area of high concentration (low solute concentration) to an area of low concentration (high solute concentration). This passive form of transport is one that involves a semi permeable membrane. We humans and other animals contain many cells, and these cells all have a permeable membrane in which diffusion/osmosis occurs. This movement of water is vital to our lives. Focused Problem I will investigate how the concentration of salt in water (moles) will affect the rate of osmosis. ? This will be observed by placing a cellulose bag (or "cell") into a beaker concentrated with salt. The rate of osmosis will be observed by first weighing the cellulose bag's initial mass, and after the 24 hour time period, the final mass will be measured to see just how much the concentration of salt affects the rate of osmosis across the semi permeable membrane. Therefore, by finding out what concentration produces what results, we can apply this to instances where we might want to alter the rate of osmosis to benefit us. ...read more.

Middle

mass of the Dialysis bag /g � 0.01g Final mass of the Dialysis bag /g � 0.01g Initial mass of the Dialysis bag /g � 0.01g Final mass of the Dialysis bag /g � 0.01g Initial mass of the Dialysis bag /g � 0.01g Final mass of the Dialysis bag /g � 0.01g Initial mass of the Dialysis bag /g � 0.01g Final mass of the Dialysis bag /g � 0.01g Trial 1 10.85 10.85 10.65 9.10 9.20 7.06 10.08 6.41 10.15 6.64 Trial 2 9.83 9.78 9.60 8.60 9.00 7.98 9.88 7.13 10.42 7.05 Trial 3 9.71 9.78 9.51 8.40 9.10 7.88 9.88 6.67 9.40 6.22 Trial 4 9.63 9.60 9.46 8.20 9.40 7.34 10.09 6.78 10.19 6.70 Trial 5 10.67 10.62 10.41 9.10 9.10 7.11 10.47 7.20 10.31 6.11 ==>Table 1 shows our collection of data, in which we recorded our initial and final mass of the cellulose bags for each trial and each concentration of our experiment (5x5). Table 2 - Differences in Mass Measurements for Dialysis Bag containing various concentrations (+0.85-0.86 M) of salt after being placed in 500ml of distilled water for 24 hours Concentration /M � 0.01 M 0 0.86 1.71 2.57 3.42 Trial 1 0.00 -1.55 -2.14 -3.67 -3.51 Trial 2 -0.05 -1.00 -1.02 -2.75 -3.37 Trial 3 0.07 -1.11 -1.22 -3.21 -3.18 Trial 4 -0.03 -1.26 -2.06 -3.31 -3.49 Trial 5 -0.05 -1.31 -1.99 ...read more.

Conclusion

One smaller factor of "weakness" could have been the time of putting the cells in the beaker. Since we are school students, it is near impossible to take out our bags in exactly 24 hours, but if we could, it would help us get better results. An extra 10 or 15 minutes may not seem like a lot of time, but it may have a bigger meaning in the rate of osmosis. Improvements The biggest improvement would be to use some other material other than cellulose tubing to do our experiment. I feel that all the cutting and tying makes the cellulose tubing a lot weaker, as we are constantly touching it and probably making the material weaker and slightly more "permeable". This I feel changes osmosis rates drastically. Using other semi permeable materials other than the cellulose tubing will probably improve the accuracy in our results. I saw some other people mention and experiment with cucumbers, and I feel that something like that will be a better item for use in this experiment. Personally I felt that 24 hours was not enough time to really see and analyze the rate of osmosis. Ideally, I would like to extend the time of observation from 24 hours to something around 72 hours for each experiment. I think increasing the observation time will allow osmosis to "fully" happen and will help us attain better and more accurate results. ...read more.

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