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Finding out the effect of osmosis on potato chips at different concentrations of sucrose solutions.

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Introduction

Investigating the effect of sugar solutions on potato chips Aim In this investigation I will be finding out the effect of osmosis on potato chips at different concentrations of sucrose solutions. Prediction Osmosis is defined as the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration. In a high concentration of water the amount of solute (e.g. sugar) is low. This could be called a weak or dilute solution. In a low concentration of water the amount of solute (e.g. sucrose) is high. This could be called a strong or concentrated solution. When two such solutions are divided by a semi-permeable membrane the water will move from the area of high concentration to the area of low concentration, until both sides are equal (have reached equilibrium). Weak solution partially permeable membrane Strong solution The solute molecule sugar is too large to diffuse through pore in the membrane. Water molecules small enough to diffuse through easily. Temperature can affect this by speeding or slowing down the process so we will try and keep the temperature the same. Net diffusion of water Knowing that osmosis will occur across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane, and knowing that when this happens to cells they will either become turgid if water flows into them, or plasmolysised (when cytoplasm is drawn away from the cell wall) if water flows out of them, and thus change their volume, we want to test the hypothesis that: Plasmolysis Cell membrane The vacuole shrinks and water passes out of the cell by osmosis. The gap between the cell wall and membrane causes water to pass out. The cytoplasm starts to peel away from the cell wall and has undergone plasmolysis. Cytoplasm If the concentration of a solution into which a cylinder of potato is placed is greater than a certain level the cylinder will contract, and if the concentration is less than that level it will expand. ...read more.

Middle

Using a razor blade I peeled the potatoes and cut each one into an even block approximately 5cm by 1cm by 1cm on a white tile. Then I used a razor blade and ruler to cut the potato into chips, which were 5 cm long. I was very careful whilst cutting the potato, as the blade is exceptionally sharp. I then had 15 chips. Taking a test tube rack I placed 10 test tubes and then labelled them distilled water, 1.25%, 2.5 %, 5% and 10 %. Using a measuring cylinder I measured out different amounts of sucrose solution (20ml) and distilled water, which I then poured into the test tubes in a percentage ratio giving me the various percentage concentrations. In my planning I said that I would weigh the potatoes but unfortunately they were not available for this investigation. I then swiftly put 1 potato chip into each beaker and then waited for osmosis to occur. I then left it for a day. The next day I drained out the solutions in the sink and placed all the chips on the paper towel in the order I had put them in the test tubes as to not confuse myself as to which chip came from which solution. I dried each chip carefully with a paper towel and then recorded how each potato increased in mass as to see if they increased or decreased in size with a ruler. Whilst doing this I made sure I worked safely. I used a very sharp razor blade, and made sure I used it carefully as it could injure someone if it's not handled properly. Also while I used the blade everyone wore safety goggles. And I was also careful with the solutions that they don't get into our bodies internally, just in case, because we are not fully aware of the damage it could do to us. ...read more.

Conclusion

In some cases we were finding it hard to finish the investigation in time so I would have preferred to have more time so we could had have more time preparing and less room for mistakes and under strict time it was hard to get perfect results. Overall I think the investigation worked really well as my results and graphs are quite accurate as I made the investigation fair as possible by repeating the investigation twice and using the right equipment to make it safe. My results were accurate and completed twice to assure a higher quality result assuring us that our results were even more accurate. Our results were very similar so it proves that we carried out the investigation carefully so that we achieved good results. The accuracy of the experiment was accurate to suit our purpose to make it more accurate several steps could have been taken. 1: Human error: Human error could have been reduced by taken more accurate measurements to a uniform result. This could be attempted by using a tool which could be set to a set length to cut the potato. 2: Instead of the range of the potato being 0.0 to 0.30 the range could be decreased to 0.20 to 0.30. This would produce more accurate results. Also increasing the number of results so instead of taking results from 7 different molarity levels 10 molarity levels could be taken. This would make the lines of best fit on the graphs more accurate, therefore the end results would be more accurate. 3: If the potatoes did not rest against the sides then they would all have the same amount of surface area. This is the same for the potato samples that float therefore exposing themselves to air and the samples that sink stopping osmosis occurring on the areas that are touching the bottom of the test tube. Reliability: The results were reliable to take a reasonably accurate result. However the steps above (1,2 and 3) would produce an even more accurate result. 2 ...read more.

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