Scientific Knowledge
Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.
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Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.
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Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.
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Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.
If a selectively permeable membrane separates the two solutions, water moves through it in both directions at the same time. However, more water leaves a dilute solution (high water concentration) and passes into a more concentrated solution (low water concentration) than enters it. Although the water appears to move across the membrane in one direction, it is in fact moving in both directions but more one way than the other.
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A potato’s cell has a fully permeable cell wall, but a selectively permeable cell membrane, which allows certain substances to enter and not enter the cell, such as water and sucrose in this instance. In all things, everything moves from high concentration areas to low concentration areas, when in water; this process is called ‘Osmosis’. With potato (plant) cells, it swells up as water enters via osmosis, however, it won’t burst because the cell wall is tough, and it only stretches out slightly. When it can’t stretch anymore, it is called ‘Tugor’; this is what makes the plant firm and stands up. The opposite, when the cell membrane shrinks to its limit because of lack of water, is called ‘Plasmolysis’, which makes the plant, wilt.
Analysis of Graph
The graph shows a clear indication that there was a percentage change in mass in mass of the potato chips over the course of the hour experiment. The graph is a smooth curve that slopes downwards and passes though the origin, it means that the percentage gain and loss in mass and concentration are directly proportional. For example if you double the concentration, the mass of the potato will double. The graph shows that the X axis goes though the origin.
From studying my graph I can clearly see that there is only one anomalous and that is at 0.8 m/mol because it would be too heavy (too much water). Otherwise my graph is accurate and all of my other points go though my curve.
My graph and the results show that:
- Osmosis actually took place in the experiment
- As the molars increased, the difference decreased
The gradient of my graph does not change, it get less steep as the ‘X axis’ gets bigger, this is because the potato chip is becoming flaccid, and so the change in mass of each molar concentration is becoming closer together because there is a less weight change.
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Conclusion
“I predicted that as the concentration increased, the weigh of the potato will decrease”, has proven to be right. The reason for this is because that osmosis will make water molecules move from a high concentration to a lower concentration. To conclude this up, I can say the movement of the water though a selectively permeable is affected by the concentration of the solution. The higher the concentration of the solution, the more the potato chip will lose weight. Basically, as the concentration of solution increases, the water is less able to move to the potato, causing the water from the potato to move to the solution as therefore will be decreasing its weight. In this experiment, I believe that I have collected enough data to support my prediction. Having the results and the graph which backs up my prediction, it proves that this investigation was fully successful.
From the scientific knowledge which I collected, I can say this experiment was successfully carried out in the process. The reason behind this is that the potato has selectively permeable membrane separates the two solutions, water moves through it in both directions at the same time. However, more water leaves a dilute solution (high water concentration) and passes into a more concentrated solution (low water concentration) than enters it. Although the water appeared to move across the membrane in only one direction, it is in fact moving in both directions but more one way than the other.
In the living cell, both the cell wall and plasma membrane determine the permeability of the cell. The capability of a substance to pass through these barriers is known as the permeation of the substance. Since not all substances may pass into or out of the potato, this is known as selectively permeable or as a semi permeable membrane. The semi permeability varies from cell to cell and under certain conditions for we changed the concentration. The water will diffuse into the cells, making it turgid. This would explain why potato put into a solution of 0 molar seemed very firm compared to the potato used for 1 molar, this was because the cells of the potato had lost their turgor, and had become flaccid.
As water molecules have kinetic energy, they are constantly moving around in gaseous or liquid form, moving randomly from one place or another. The greater the concentration of water molecules in the solution, the greater the kinetic energy. This means, that as the concentration of salt increases in a solution, the concentration of water decreases. Relating this to the potatoes: basically, as the concentration of salt in each solution increases, the water in the solution is less able to move to the potato, causing water from the potato to move to the solution therefore decreases weight.
Evaluation
The experiment was very successful in my opinion. I obtained a large quantity of very accurate results from which I was able to create a very good graph. I think I took enough results for the amount of concentrations that I was using and the time that I used for the experiment, which the potato was in the solution for was enough to allow sufficient amount osmosis to occur.
I was also pleased with the results which I obtained from my experiments, because they proved to be accurate as my repeat readings were also very close to each other.
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The cutting of the potatoes was the most difficult part of the experiment because I was recording my results by mass. If I were to repeat the experiment I would have possibly find a machine to cut the potatoes in cylinders, as this would ensure that all the potatoes would be the same weight. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each spearmen tube. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.0000g. (However this would be hard to get it accurate)
When weighing the potato chips after I hour in solutions, it was predictable that they would have excess water on them, and so we dabbed them with paper towel to remove it. However, in doing this we could have removed water that was not excess, and altered our results. Also it was hard to use the same process each time, like roll them a certain amount of times and different pressure for each potato. I would suggest using a hair dryer at a low pressures for a small amount of time only, using the stopwatch.
Another inaccuracy was when we put the potato chips into the solutions, because you would have to leave a small interval, because at the end you would have not had enough time to dry the potatoes, because the other one was over 1 hour. To resolve this suggestion was to allow about 3 people to carry out the experiment together.
As studying on my graph I had one main anomalous point, the reason behind this is all of these explanations above, also the main point might have be human error, like misreading the weight and write down the wrong figures.
Also another reason might that we have forgotten to damp down the potato because we were under time and pressure, the reason for this is that the graph shown that the potato was too heavy compared to the rest. Maybe also the top pan balance was not cleaned every time, otherwise there would have been excess water and fragments of the potato on the balance, which could had an effect on the results.
However if I was to repeat the experiment I might well increase the time of the experiment to allow more time for getting more accurate results and completing the experiment in a slower process.
The range of concentrations was enough but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results, i.e. 0.0, 0.1, 0.2 etc… instead of 0.0, 0.2, 0.4 and so on in an attempt to achieve more accurate results. I could also introduce other variables such as temperature.
Another problem was the fact that I was forced to rely on inaccurate tools to cut the potato cylinders such as scissors, scalpels and my own judgement. Yet another complication is that there is no guarantee that each potato was the same density throughout the experiment, in fact it is highly unlikely.
Finally another idea is try other similar vegetables such as sweet potatoes, carrots, turnips and parsnips, to see the different type of osmosis which is happening and also then compare the results.
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