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My chosen variable is the concentration of sugar in the solution.

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Introduction

My chosen variable is the concentration of sugar in the solution. I predict the higher the concentration of the salt solution (sodium chloride) the more mass the potato chip will lose. This is because of Osmosis. Osmosis is the movement of molecules from a dilute solution (potato chip) to a more concentrated solution (salt solution) regulated by a Semi Permeable Membrane. The salt solution has a low concentration of water, while the potato chip contains a high concentration of water, compared to that of the salt solution. The Osmosis is removing the water from the potato chip so that it can go into the salt solution, because it is trying to create equal sides, but this can never be achieved since the Semi Permeable Membrane will not allow the Sugar molecules to pass through. I predict that the higher the concentration of salt solution, which the potato is placed in, the more the potato will decrease in size. This means that the lower the concentration of salt solution the more the potato will increase in size. I predict this because I know that osmosis, the movement of water molecules, takes place from an area of low solute concentration to an area of high solute concentration. If you place a piece of potato in a high concentration of sucrose solution and leave it for 24 hours the water molecules in the potato, which is a low solute concentration compared to the salt solution, will travel through the semi-permeable membrane into the high solute concentration of the salt solution. As the water molecules have diffused from the potato and into the salt solution it results in the potato chips loosing molecules and decreasing in length, size and mass. However if you place a piece of potato in a low concentration of salt solution the opposite will happen. The potato is now the area of high solute concentration because the salt solution is much weaker as it has more water present because it is a lower concentration. ...read more.

Middle

The results I have got, to my understanding and knowledge is completely fair. Because I have carried out my experiment using the right method and all the safety issues are employed in my experiment. I have used the same amount of sodium chloride solution in all the test tubes; I have left the potato tubors in the solution for 2 days in all the test tubes. And most importantly I have measured and weighed out all the potato tubors so they are all of equal length and mass. The data that I have obtained from my experiment is shown below. I have put my results in a table so it is easier to reveal the changes in length and mass after the tubors have been placed in their respective solutions for 2 days. Concentration/Molarity Potato Masses Before Potato masses after 0M 0.04g 0.05g 0.03g 0.22g 0.26g 0.19g 0.5M 0.05g 0.05g 0.02g 0.15g 0.16g 0.15g 1.0M 0.05g 0.03g 0.04g 0.11g 0.12g 0.10g 1.5M 0.06g 0.05g 0.04g 0.04g 0.02g 0.04g 2.0M 0.03g 0.04g 0.05g -0.01g 0.00g 0.01g 2.5M 0.03g 0.04g 0.05g -0.03g -0.05g -0.08g I have obtained these readings after 2 days of allowing the tubors to be placed in their test tubes. I have then collected them, dried them using tissue paper and weighed each individual tubor on a weight scale. The new mass of each tubor can then be compared with its mass reading. This new mass can then be compared with its original mass and thus with this information compiled together, I will be able to analyse what has really happened and whether the experiment of osmosis has occurred or not. How to find out the percentage difference in mass. Concentration/Molarity Potato Masses Before Potato Masses Before (Average) Potato masses after Potato masses after (Average) 0M 0.04g 0.05g 0.03g 0.04g 0.22g 0.26g 0.19g 0.22g 0.5M 0.05g 0.05g 0.02g 0.04g 0.15g 0.16g 0.15g 0.15g 1.0M 0.05g 0.03g 0.04g 0.04g 0.11g 0.12g 0.10g 0.11g 1.5M 0.06g 0.05g 0.04g 0.05g 0.04g 0.02g 0.04g 0.03g 2.0M 0.03g ...read more.

Conclusion

With a decrease in temperature, then the rate of osmosis also decreases and so perhaps the temperature was not kept at a constant during the entire experiment. Furthermore, perhaps the tubors used were irregular, that is, perhaps they were not perfect cylinders. In this case, the amount of water that enters may differ and thus the total mass of the cylinders will differ. These are the most noticeable errors. The way my experiment could have been improved could been in many ways. The first way to improve my experiment would be to take into account these noticeable errors and overcome them to make my experiment more reliable. Now, in order to keep the temperature constant, I will keep the test tubes containing the tubors inside a stored area, where the temperature is kept constant always; this will prevent the chance of any change in the rate of osmosis and it will prevent any inaccuracies in the mass readings. My experiment can be improved further more by using a different range of concentrations of salt solutions for more exposed changes in mass of the potato tubors when placed in these solutions. Maybe I could use 0M, 2M, 4M.... and so on. Another way to improve my experiment is by thinking whether the period of time the osmosis was taking place. Was 2 days too long or too short? I could find this out by more research. If I were to redo the experiment I would take a lot more care in accuracy of data and to expand my experiment I would carry out my experiment to the most of 3 times. In conclusion, I have found out that when a substance is placed in a more concentrated solution, it loses water in order for equalization to occur and thus in the case of the potato tubors, they will decrease in mass. Furthermore, when placed in a less concentration solution, the tubors will gain water in order for equalization to occur and so they will increase in mass and length. ...read more.

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