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Determine the water potential of potato tuber cell with the varying affect of solute concentration

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Introduction

:)Determine the water potential of potato tuber cell with the varying affect:) :)of solute concentration:) Introduction:) This investigation will try to determine the water potential of potato tuber cells. This will be carried out by using a potato cylinder and bathing it in different solutions of solute with different molarities and distilled water, which is pure. We will be able to find the water potential of the potato tuber cell by finding on the graph the equilibrium point where no water enters or leaves the potato. Osmosis has a very important role in this experiment. It is safe to say that osmosis is a unique type of diffusion, however only concerning with water molecules when they pass through a partially permeable membrane. When talking about the components of osmosis, the solvent (the water) and the solute (the sugar) added together make up the solution. In osmosis we always have a partially permeable membrane (the potato). It is known as this because it only allows certain molecules pass through like in our case the water molecules, just like a membrane in real life. Looking at the diagram below, we can see that sample 1 has a lower concentration of solute molecules which means it is a more dilute solution since there is a higher concentration of water molecules. Sample 2 is more concentrated since there are more solute molecules. If all the molecules could pass through the membrane, there would be a net movement of solute molecules from 2 to 1 via diffusion due to the higher concentration of solute molecules in sample 2. The solute molecules would go in between the spaces available which is why there would be a net movement. Partially permeable membrane Water level Water molecule Solute molecule 1 2 We know that only the water molecules can pass through the membrane so what was said above would only count if the membrane was removed. ...read more.

Middle

Another error that preliminary work showed was in the potato cylinders. From my previous results it is clear that the initial masses of all the cylinders were different. This means that cylinders with a larger mass would have a different amount of osmosis than the smaller ones due to the increased surface area. The larger surface area means that more osmosis can take place so to compare the potatoes would be unfair as they are not all the same. A correction for this mistake would be to make sure that the potatoes have the same mass or as close as possible. An error which also present is heat and light. The solute solutions are given to us. This means that they may have been left open in the light for a while which means that the heat has had enough time to evaporate some of the solutions. As this happens the concentrations of the solutions changes and becomes more concentrated as more water is taken away. A way to correct this error is to ensure that the solutions are made personally and that they are concealed and kept cool. In the final evaluation of this investigation, these errors will be looked at in more detail. (The need for safe working) Safety is very important in this experiment even though the experiment seems to be relatively safe. This is why it is taken into consideration. A very sharp knife is going to be used which could seriously hurt someone if it is not handled with caution and care. Also, caution must be taken to make sure the solutions are not swallowed because we are not fully aware of the damage it could do to us. Plus some other harmful chemicals from other experiments could be mixed with the solution somehow and can seriously harm us. Goggles should also be worn to make sure no acids from previous experiments harm your eyes, or so that you don't cut your eyes with the knife. ...read more.

Conclusion

Not only this but further work could be carried out to include concentrations that increased in 0.05 M rather than 0.2 each time. Even though my graph is very accurate (hand drawn plus small intervals) this would increase the accuracy and improve the graph. Other investigations could include using different varieties of potato or different plant tissues e.g. carrot, apple, pineapple, strawberry and tomatoes. I could also extend this experiment by repeated exactly as before to get an average. However this time I could take more results at the molarity levels from 0.00 up to 0.20 in single digits then 0.21, 0.22, 0.23, all the way up to 1.0 M. This would produce much more accurate results. This is going into much further detail but is required for more scientific knowledge and accuracy. Other variables in the experiment could be changed such as instead of changing the mass of the potato, the species of the potato could be changed. For example a new potato, a really old potato, a different kind of potato or even a different vegetable could be used. Also the shape and size could be changed. However this would not affect the results much. This is because the variable would only change the rate of osmosis because of a different weight and size. We could have used potato discs which would give much more surface area plus more accuracy. Even liquidised potato could be used for the same reasons. For even more demand for accuracy the temperature could be changed. For example the samples could be placed in different water baths and brought up to different temperatures. This would see if temperature played a part in the osmosis of potatoes. A preliminary experiment could be set up beforehand to find out how long the experiment should be kept going because if the concentration of the potatoes equalises then the weight of the potatoes will be almost exactly the same. But overall, given the apparatus that I got to carry out the test, I think this experiment turned out to be very successful, and I'm very please with my results. ...read more.

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