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Our set task was to investigate the change in weight gain or loss in a chosen size of potato, once it had been soaked in test tubes containing varying concentrated salt solutions, to study Osmosis.

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Introduction

Steven Gregson 11I Osmosis Coursework Our set task was to investigate the change in weight gain or loss in a chosen size of potato, once it had been soaked in test tubes containing varying concentrated salt solutions, to study Osmosis. Research Osmosis is a special kind of diffusion, when the passage of water molecules from a weaker solution into a stronger solution, through a semi-permeable membrane. A semi-permeable membrane is one that allows small molecules through it, but not larger molecules such as sugar. We used a cork borer to get the width of the potato pieces the same width, but cut them free hand without measuring them to approximately the same size. We then weighed them each individually before we put them into the solution so that we would know the gain or loss of the potato at the end of the experiment. We were using a varied range of salt solutions, with a H20 (water) solution too. So that we had different concentration levels. Apparatus * Potato * Cork Borer * Chopping board * 5 boiling tubes * Scalpel * Top- pan Balance (accurate to 2 d.p) * Measuring Cylinder Information on making it a fair test In order to make the experiment a fair test, we have to take these few things into consideration: * Temperature * Size of the Potato * The light in the room * Type of Potato * Amount of time left in solution * Using the same Scales ...read more.

Middle

I will then fill each boiling tube up with one of the different concentrated solutions and put the pieces of potato in each. I controlled the amount of solution going into each by measuring it first in a measuring cylinder. This will make it a fair test. I will then leave them to stand for 25 minutes, without having any further contact with them until the experiment was over as this could affect my results. Prediction I predict that as the salt concentration increases the weight loss of the piece of potato will also increase. I think this because as the concentration strength increases more water molecules will pass from the potato into the water through the semi-permeable membrane, to try and equal the strengths of both the potato and the salt water solution. So this means that the opposite will occur when the salt solution is decreased. Observation during the Experiment When I had put the potato chips into the solutions, they all sank to the bottom immediately. However after approximately 5 minutes, the potato chips in the 14 and 20% solutions had risen to the top of the solution. I was surprised by this, so I watched the experiment more closely than I had intended too. After another 7 minutes, both of the potato chips had sunk back down to the bottom of the boiling tube. ...read more.

Conclusion

My final results proved my prediction to be correct. The results that I had may not of been 100% accurate though, as on taking them out of the boiling tubes they were only rested on top of a paper towel to take the excess liquid off them, so some of the potato chips may have still contained some of the liquid affecting it's weight. If I had of had more time, or I did the experiment again, I would ensure that I had dried out fully, or made sure that the potato chips had of been drained for as long as one another, making it more of a fair test. So that none of the liquid could affect the weight of the potato chip as it might have done. If we were told to research osmosis more, I would not repeat the same experiment exactly. I would use stronger concentrated solutions, as repeating the same experiment would not vary the results as much. Also leaving the experiment for a longer length of time may benefit the amount of weight gained or lost, showing a stronger set of results. Despite not using these factors, the results I got were very strong and correct. Within the time that we had to do this experiment, the results came out stronger than I had anticipated, but still proved my predictions to be correct. Even though I did not expect the potato chips to lose or gain as much weight as they did, they did not affect my prediction, making it wrong. ...read more.

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