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Investigating water movement in potatoes.

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Introduction

Investigating water movement in potatoes Aim The aim of this experiment is to find out of potatoes lose or gain weight in different strength solutions. Background Osmosis is the movement of water molecules through a particularly permeable membrane from a weak solution to a strong solution. We did some preliminary work, an experiment where we placed visking tubing with sugar solution into a beaker containing water. It was absorbed and the tubing blew up. This demonstrates osmosis when the visking tube contains water. We then put a piece of potato into each solution, we left it for 30 minutes and if it went hard we know it has been in a weak solution. A turgid cell is one that has gained water. A flaccid cell is one that has lost water. If a turgid cell is next to a flaccid cell then the flaccid will gain some of the turgid cells water. The potato that has the highest osmosis concentration will gain water and therefore weigh more. Prediction I think that the stronger the solution, the less the potato will weigh. ...read more.

Middle

Then you need to weigh all your potato pieces again and make a note of each of the results. You must then repeat this until you have done the experiment 3 times. Fair test To ensure that this is a fair test I need to control some things like the size of the potato pieces, each potato must be of the same shape and same size, the potato pieces should be cut from the same potato to ensure that it is not bias. If this is not possible then the potatoes should be of the same type and from the same date. The potatoes should be of a recent date so that they are fresh and can take in water. The temperature must be kept the same in the experiments as this would be another variable and we don't want that. As mentioned in the method each different strength solution should be of the same amount. The time must be too. The same balance should also be used for the weighing of the potato before and after, as the scales may be slightly inaccurate so we want to make sure that the potatoes have been weighed with the same scales. ...read more.

Conclusion

As osmosis is the movement of water molecules through a particularly permeable membrane from a weak solution to a strong solution it is clear that osmosis has taken place. Evaluation I think that my experiment went quite well as most of the results seem accurate, I think that they are accurate too as we repeated the experiment, we did it 3 times, but it wasn't all accurate as you can see from the results as there was an anomalous result; this result is most likely wrong because we probably forgot to take the surface water off. This experiment was safe as no one was injured. Although I did not find the method particularly hard it was slightly hard trying to get all the potato pieces to the same length. If I were to do this experiment again I would repeat each experiment more times and I would eliminate any anomalous results before working out the average % weight change. To further support what I have found out in this experiment I could have used different vegetables or I could have also recorded the lengths of the potato before and after putting them in the different strength solutions. ...read more.

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