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The effects of different salt solutions on potatoes

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Introduction

The effects of different salt solutions on potatoes Plan My aim is to investigate how different concentrations of salt solution affect the movement of water through a partially permeable membrane (osmosis) in potatoes. Osmosis is the movement of water from a high concentration to a low concentration through a partially permeable membrane. I will add pieces of potato to varying concentrations of salt solution, wait on each solution and then record the results. I will eventually use the results to measure the percentage change in mass of the potatoes. To gain accurate results, I will have to make the experiment a fair one, to do this I will implement the following: Wash my hands before preparing any potato samples. -So no grease, dirt or any salts transfer from my hands to the potato pieces before the experiment takes place. I will take core samples from the potatoes. -To ensure maximum surface area for the salt concentration to cover. Make sure that only my variable factor changes throughout the experiment and other factors stay constant. Wash all equipment before using them - To make sure no residue left on them affects the results. There are several factors that would affect my experiment, the paragraphs below identify these factors and explain how I will keep them constant. - My variable factor for the experiment is the salt solution. I am aware that the experiment will be affected by certain factors; I will try and keep these factors constant so the end results will be accurate and therefore conclusive. Surface area would affect the rate of osmosis because the greater the surface area the more area the water has to diffuse through. ...read more.

Middle

9. I will then analyse and evaluate the whole experiment. I will repeat the experiment 3 times in order to get a more varied set of results, which will be more useful in showing the results to be accurate. I will leave the potato cores for 180 minutes because I believe that leaving them for any shorter period would mean that osmosis would not have happened fully and therefore I would get inconclusive results with a large margin of error. My range of concentration will be from 0% salt solution to 1.8% salt solution. Safety Even though this is a fairly safe experiment, safety precautions must be taken in order to prevent physical damage to the body. Be cautious when using the scalpels or corers as there are sharp metal edges exposed. In case of any breakages of the glass beakers, the teacher must be informed straight away and the glass cleaned away as quickly as possible. Syringes must be used safely and only used inside measuring containers to extract or deposit solutions. The table below shows the concentrations of water and salt solution in 10 concentrations. Final concentration of 20ml3 salt solution% Volume of water ml3 Volume of 2% salt Solution ml3 0 20 0 0.2 18 2 0.4 16 4 0.6 14 6 0.8 12 8 1.0 10 10 1.2 8 12 1.4 6 14 1.6 4 16 1.8 2 18 Results For 1st experiment Concentration Of salt sol. % Diameter of potato Change in Diameter of potato mm % change in diameter of potato Time=0 Full time 180mins 0 11.1 11.1 0 30 0.2 11.2 11.65 0.45 65 0.4 11.8 12.3 0.5 10 0.6 11.5 11.1 0.4 10 0.8 11.6 11.8 0.2 -25 1 11.9 11.3 0.6 -150 1.2 ...read more.

Conclusion

Also, because of the safety measures that I used (like washing my hands and all equipment before use) - I was able to decrease the margin of error and therefore increase the accuracy of the results. I know that my method must have been a fairly good one because of the accuracy of the results and how they agree with my conclusion. The prediction agrees with the results as well as the conclusion, so I know that the results must be fairly accurate. Apart from the general margin of error that meant that none of my graphs were completely similar, there was one very erroneous result taken on the 3rd experiment (circled on the graph). I think that this could have happened because all cores were not completely cylindrical, the diameter varied at different points along the sample. This would have meant that readings might have been taken from different points along the core before and after the experiment - giving inaccurate results. Because of the nature of the thing I was trying to measure (potato cores) and the difficulty of being completely accurate, it has led me to believe that maybe measuring another factor that would have changed as a result of different salt concentrations like the mass of potato cores. This would have given me more accurate results, as there wouldn't have been any problem with measuring by hand at different points. Also, digital scales would have preformed all measuring, which would have been far more accurate. To reduce error on measuring the diameters of the potato, I could have taken at least 3 diameter readings from each core and found the average diameter size to use in my results, but this would have been too time consuming under the circumstances. ...read more.

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