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An Investigation of Factors Affecting the Rate of Osmosis.

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An Investigation of Factors Affecting the Rate of Osmosis Introduction Osmosis is the movement of water molecules across a semi permeable membrane from a region of high water concentration to a region of low water concentration. A semi permeable membrane is a membrane with very small holes in it; they are so small that only water molecules can pass through them. Bigger molecules such as glucose cannot pass through it. In actual fact water molecules pass both ways through the membrane, but because there are more water molecules in the high concentration region than the other there is a steady net flow into the lower concentration region. The lower concentration is the stronger solution, such as a glucose solution. This movement causes the glucose-rich region to fill up with water. The water movement is diluting the solution so that the concentration on both sides is equal. This diagram illustrates the net flow of water movement from a hypotonic solution, low solute concentration, to an area of high solute concentration. In other words this shows water movement across the semi permeable membrane from a high concentration of water to a low concentration of water. Water moves from a high water potential to a low water potential. A low water potential is a high solute concentration. Water potential has the symbol ?, sigma. When water potential on both sides is equal then it is known as equilibrium. In this case there is not an absence of movement between the equal water potentials but a movement of water in both directions, maintaining the equilibrium. Osmosis is a continuous process which does not require any energy to take place. Factors Which Affect the Rate of Osmosis 1) Temperature: The higher the temperature is the faster the molecules will move. This means that the movement of water molecules across the semi permeable membrane will be faster. 2) Surface Area: When there is a larger surface area there will be more space for the molecules in and so they will be able to move across more easily. ...read more.


Every five minutes take the potato samples out and weigh them, then put them back into the beaker, and record the weight * Continue to weigh the samples at 5 minute intervals for 30 minutes Problems Encountered and How to Solve Them The preliminary experiment helped me very much in conducting my final experiment. My preliminary experiment had many errors which I identified and corrected in my final experiment. Firstly I didn't use the 0M solution; this was because this solution had run out as many people were not economic in pouring it into the beaker. This can be solved by using only the amount needed in your experiment and pouring the solution cautiously as to avoid spilling any. I did not in this experiment use more than one potato sample, to check if my results were consistent or if they were a one off. Therefore in the final experiment I will take more than one sample at each solution. Practically doing the experiment was a huge rush when it was time to weigh the potato sample. I did not put each potato sample in at different times, meaning I had to weigh them all at the same time, which was not possible. To overcome this in the final experiment I will put first sample in, and then wait 1 minute before putting in the next potato sample. By doing this I will have enough time to weigh all the potato samples correctly. Also I have decided to take the weight reading every 10 minutes. This is due to the fact that measuring the weights every 5 minutes was too chaotic and could easily lead to errors. Also by staggering the time of weighing the samples taking the last sample of the first five minutes would overlap with taking the first sample at the next five minutes. Therefore it would not be possible to take the sample every 5 minutes. ...read more.


Therefore you could have easily missed your time to put the sample back into the beaker. Also another problem was drying the potato samples. This is because there was no way whether we could be sure if we had dried all the samples equally. Some samples may not have been dried enough and other may have been dried too much. Doing this would give rise to anomalous results. To carry out the experiment safely it was imperative we were extremely cautious when using the scalpel knives. This could have easily cut someone. To further improve the experiment we could conduct it with a longer time limit, so that we can specifically see how long it takes for the samples in different solutions to reach equilibrium. Hypothesis I believe that the higher the concentration of the solute the longer it will take for it to reach equilibrium. Method * First get six beakers and label them all accordingly, from OM (distilled water) to 1M in 0.2 intervals. * Now measure 40cm3 of each solute into each appropriate beaker * Get a potato and a cork borer of appropriate size, if the potato small you cannot have a large size cork borer as you will not be able to get enough potato cylinders from the potato * Cut the skin off the potato cylinders as the skin is not homogenous * Weigh the potato and make sure all the samples are off similar weights and shapes * Now put the first cylinder into the 0M beaker and begin to time, after ten minutes put in the next potato sample into the 0.2M beaker. Continue to put in the samples into the beakers in ascending order, until there are none left * Every hour measure the sample, by taking it out and then drying it, weighing it and putting it back into the beaker. This should be done for until all the solutions have reached equilibrium I made the time interval an hour because it is clear this experiment would take much longer than the previous one. ?? ?? ?? ?? ...read more.

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