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Preliminary Osmosis.

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Introduction

Preliminary Osmosis Exp. 1 Aim: To find out a suitable time to leave the potatoes in the solution for. Apparatus: 4 boiling tubes, stop clock, boiling tube rack, 2 potatoes of similar height, potato borer, scales, Pure water, 80 % sucrose solution Method: ? Put on goggles, collect apparatus ? Cut potatoes into 4 cylinders ? Weigh potatoes and record mass ? Place 1 cylinder into each boiling tube. ? Measure 30cm� of pure water 2 times and pour into 2 boiling tubes. ? Immediately Start Stop Clock ? Repeat Steps 5and 6 using 80% sucrose solution ? Take out potato cylinders from solutions ever 10 minutes, blot and weigh, record the weight. Time Pure Water Sucrose 80% A B A B 0 1.410 1.370 1.360 1.480 10 1.560 1.400 1.220 1.310 20 1.490 1.420 1.130 1.200 30 1.500 1.440 1.090 1.150 40 1.500 1.440 1.040 1.100 Change +0.09 +0.07 -0.320 -0.380 Conclusion There was an increase in mass in the water because there is less water in the potato then solution so the water travels from where there is less to where there is more, the potato - this is called osmosis. Potato in 80% sucrose decreased in mass because the water travelled from the potato to join the sucrose concentration as there was less water in the solution then the potato - This is called osmosis. ...read more.

Middle

I know this because like my introduction states, the water will travel into the potato to try and join with the sucrose solution. Through my preliminary work I also found out that the sucrose concentration inside a potato was between 0% and 10%. Using that knowledge I predict that the potato in the lower amounts of solution will increase in mass and decrease in mass when the amount of sucrose is higher. Apparatus: 10 boiling tubes, 2 boiling tube racks, bottles of sucrose solution (2%, 4%, 6%, 8%, 10%) 1 large potato, or two of the same height, stop clock, potato borer. Fair Test: To keep it a fair test, all the boiling tubes are in the same temperature water so it does not affect the experiment, there will always be the same amount of sucrose concentration in each boiling tube so that that does not affect the experiment either. Those two variables would speed up the rate of reaction making it unfair. All potato cylinders will be from the same potato so the same amount of sucrose will be in each one. Method: - Set 10 boiling tubes in a rack - Put 10cm3 of the sucrose concentration in each boiling tube. ...read more.

Conclusion

Our results were very accurate; there was only one anomalous point in the graph, which was the 2% concentration point. Though the line of best fit was very accurate and showed where the point should have been. The point could have been wrong, for a number of reasons; maybe we did not blot the potato enough or did not weigh it properly. To improve my experiment I would have left the potatoes overnight to give them time to fully osomosise, also completely check the weight of each potato was right and it was fully blotted before weighing. This would have maybe given more acute results. I think my results are defiantly accurate enough to support my conclusion. Almost every value fits or is very near the line of best fit on my graph. And my prediction and introduction were proved by the conclusion and results. If I were to extend the experiment I would have used the sucrose concentrations, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, this would have given much more accurate results, and I would have used 3 potato cylinders for each solution to make it absolutely fair. I would have got a much clearer idea of what percent sucrose solution is in a potato and even if one potato cylinder or two was a bit wrong the other two would have evened out the results. By Leo Matlock ...read more.

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