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An investigation into changing the concentration of sucrose soltion on the rate of osmosis in potato cells.

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Introduction

An Investigation into the effect of changing the concentration of sucrose on the rate of osmosis in potato cells. Aim-In this experiment I will be attempting to find out if increasing the concentration of sucrose in a solution will result in a decrease in the rate of osmosis. Hypothesis- If the concentration of sucrose is lower then the rate of osmosis will be higher thus increasing the mass of the potato. Furthermore I predict that when I increase the concentration of sucrose the amount of water which diffuses will decline. Taking my hypothesis into account the aim of my experiment is to investigate the extent at which sucrose solution affects the rate of osmosis. To do this I must understand which other variables will affect the rate of osmosis therefore increasing the reliability of my results and making the experiment a fair test. Introduction- Osmosis can be defined as the movement of water form an area of higher water potential to an area of lower water potential. The equation which is important when understanding water potential is water potential (?) = solute potential (?p) + pressure potential (?p).It can also be described as the passage of water from a lower concentration of solute to a higher concentration of solute. Osmosis is a process which occurs through a partially permeable membrane, which is a membrane which will only allow certain molecules through E.g. water. Diagram 1.a showing two solutions before osmosis As we can that there is a higher water potential on the left solution. Therefore the net movement of water will be from left to right until a state of equilibrium is reached. The water potential of a cell will be higher when the solute potential is lower. The net movement of water during osmosis will always move from where there's a higher water potential to a lower water potential. The highest water potential a cell can have is 0 this occurs in pure water (no ions present etc). ...read more.

Middle

* Cork borer (0.9 mm diameter)-used to produce a diameter of 0.9mm for each potato cylinder. * Measuring cylinder-to attain the correct amount of distilled water for each solution. * Volumetric Flask-used to mix both the sucrose and distilled water to the correct concentration. * 1M sucrose solution-used to combine with the distilled water to make the correct concentration of sucrose solution. * 6 potatoes of the "marfona" brand - used to take in the solution through osmosis * Distilled water-used to combine with the 1 M sucrose solution to give a range of different concentrations of sucrose solution. * Stop Watch-to measure the time the potato is exposed to different concentrations of sucrose solution. * Forceps -used to pick the potato chip out of the solution of the solution Step 1- Gather equipment and assemble into position. (figure #2) Step 2- Insert the cork borer into the potato (you should be able to make around 5 incisions into each potato). Once all of the incisions have been made you will be left with 30 different sized chips. Step 3- Using the vernier callipers and the electronic digital scales to make sure the chips are of the same length and mass. Step 4- Calculate the ratio of distilled water to sucrose solution for each solution. Ranging from 0 M to 1 M of sucrose solution, do this using a volumetric flask. Step 5- Empty the different concentrations of sucrose solutions into the 6 different beakers labelling the beakers 0.2 M etc. Step 6- Firstly put 6 chips into the beaker 0 M and after a 2 minute interval put a further 6 chips in beaker 0.2. Continue this procedure for all concentrations of sucrose solution. Step 7- After one hour of the first set of chips being in solution 0 reweigh them and record the results. After 2 minutes re weigh the other set of results. ...read more.

Conclusion

This would mean that the ratio of water to sucrose will decrease causing the rate of osmosis to decrease. Therefore in the 0 M solution there may have been a bigger increase in the mass of the potato. If I was to do the experiment again I would have made sure that the beakers were covered in cling film to prevent the air from interacting with the water. The bacteria in the air can also interrelate with the potato cylinders when they are not in the solution. Therefore the potato cylinders which are exposed to the air for longer periods of time will not gain as much water due to damage to the cells. This may be another explanation to why the higher molar valued chips gained more mass. Damage to cells may also occur when putting in and taking the potato out of the beaker using the forceps which again will cause a difference in damage to each separate potato cylinder. This will mean that anomalous results may occur causing a higher standard deviation and jeopardising the consistency of my results. However to improve my method I would use plastic forceps so the amount of pressure the cells are under is decrease, therefore there is less damage to the potato giving me more reliable findings. If I was to perform this experiment again I would increase the surface area exposed to the solution in relation to the potato's volume ratio. I would do this to increase the rate of osmosis which would therefore show a more significant change in mass. If I was to make the potatoes into a smaller disc shape it would increase the surface area to volume ratio of the chip. Also if I wanted to increase the reliability of the results I would carry out the experiment twice so I would have two different sets of results with 10 potato cylinders for each concentration. I would then take the average of the results thus increasing the consistency of the findings. ?? ?? ?? ?? Louis Jones ...read more.

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