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Osmosis Investigation - find the concentration of solutes in plant cells (potato root).

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Introduction

Osmosis Investigation Aim To find the concentration of solutes in plant cells (potato root). Preliminary Work To give me an idea of what to expect in my actual investigation, and to help me perfect my method, I did a preliminary investigation. I took two salt solutions (0.0m and 0.5m) and put 3 chips of approximately the same mass and dimensions, left them in a dry place for 2 hours, and then recorded the change in mass. I recorded my results on a table: Salt Solution (m) Chip Number Start Mass (g) End mass (g) Mass change (g) Mass change (%) Average change (%) 0.0 1 2 3 2.65 2.65 2.26 2.79 2.80 2.37 0.14 0.15 0.11 5.23 5.66 4.57 5.27 0.5 1 2 3 1.55 1.77 2.21 1.43 1.57 2.05 -0.12 -0.26 -0.18 -7.74 -11.29 -7.24 -10.11 From doing these experiments I have found out what method to use and a rough idea of what results to expect. These will also help me to make my prediction. Prediction Osmosis is the movement of water molecules across a semi-permeable membrane. The molecules travel from an area of high water concentration to an area of low water concentration. If there are two solutions with different concentrations of water, the solution with the higher concentration's water molecules will move across the semi-permeable membrane to the lower concentrated solution. Eventually, the solutions will have the same concentrations of water, although this doesn't mean the particles will stop moving across the semi-permeable membrane. ...read more.

Middle

measures out the liquids as someone else may measure them differently * Keep the temperature constant by putting the boiling tubes in the same place * Take out any anomalous results and repeat the experiment * Label the beakers so the liquids aren't mixed up Method First I will measure out the solutions and put them in the test tube and mix the solutions so the salt is spread out and not just in one place. I will then cut the chips as accurately to the same size as possible, then weigh them and put similar weights in the same test tube. Then, I will use a marker pen to number the chips to make sure they don't get mixed up. I will then put the chips in the test tubes at the same time and leave them for at least two hours to let osmosis take place. I will then remove the chips and pat them on a towel to remove any water on the outside of the chip and weigh them. I will record my results in a table. My results table Salt Solution (m) Chip number Start mass (g) End mass (g) Mass change Mass change (%) Average mass change (%) 0.0 1 0.86 1.10 0.24 27.9 25.6 2 0.74 0.92 0.18 24.3 3 0.81 1.01 0.20 24.7 0.1 1 0.79 0.82 0.03 3.8 4.0 2 0.74 0.78 0.04 5.4 3 0.75 0.77 0.02 2.7 0.2 1 0.72 0.66 -0.06 -8.3 -9.2 2 0.73 0.68 -0.05 -6.8 ...read more.

Conclusion

The only problem I had was that the marker pens used to label the chips did not work very well; this was rectified by using a different pen. Improvements I would make to my experiment is to make a template to use to see if the chips were cut to the right size, this is because when I cut the chips I had to see if they were the right size by eye and this process could have caused an inaccuracy. Changes * I could use a cucumber instead of potato as cucumber is approximately 98% water which could affect the amount of osmosis. (A potato is 0.36M water) * I could use different varieties of potatoes and see what effect this has on my results. E.g. red skin, yellow flesh, early market, chipping, Goldrush and see if this has an effect on the osmosis. * I could use seaweed, as they live in a salty habitat (the sea is around 2.6% salts). This means the cells have a higher concentration of salt and maybe this can have an effect on the mass change. * I could use different concentrations over a smaller range as this would improve accuracy and improve the graph. I could use the following concentrations: 0.05m, 0.1m, 0.15m, 0.2m, 0.25m, 0.3m, 0.35m, 0.4m, 0.45m. These would be made by mixing: Molarity (m) 0.0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Vol. 0.0m salt (distilled water) 25 22.5 20 17.5 15 13.5 10 7.5 5 2.5 Vol. 0.5m salt 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 Alex Gardner Page 1 4/28/2007 ...read more.

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