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My aim in this experiment is to find out how osmosis affects potato chips' mass when placed in different concentrations of glucose and water.

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Introduction

An Investigation into Osmosis Aim: My aim in this experiment is to find out how osmosis affects potato chips' mass when placed in different concentrations of glucose and water. Prediction: I will now predict how I think the outcome of the experiment will be. I believe that some of the potatoes will shrink and lose weight, some will swell and gain weight and some will stay the same. I think that when there is a high concentration of glucose, osmosis will occur through the potato and it will shrink as water molecules escape into the solution. When there is a very low concentration of glucose I believe the potato will swell as it gains water molecules due to osmosis trying to equal out the balance of water. I find it unlikely that any of the potatoes will stay exactly the same weight but some that are in the middle concentrations like 0.4 and 0.6 may change only slightly. However, there will be a point where the concentrations of water inside and outside the potato cells are equal (isotonic). At this point there will be no change in the length, volume and mass of the potato, as the net movement of water will be zero, no osmosis has occurred. Using this information a graph and prediction can be made. At point A the graph suggests that no osmosis has occurred, suggesting that the concentration of water inside the cell is equal to the solution outside. At point B (high water concentration), there is no indication that the cell is increasing further in size. This is because the cell is fully turgid and no more water can enter. At point C (low water concentrations), there is no indication that the cell is decreasing further in size. This is because the cell is fully plasmolysed and no more water can leave the cell. This backs up my prediction on the previous pages. ...read more.

Middle

Wipe them on kitchen roll to remove any excess moisture. 7. Weigh each potato on an electric mass balance and record results. 8. Complete a results table showing the change in weight of the potato chips. Apparatus: * 6 test tubes * Test tube holder * 6 beakers * Pipette * Tile * Knife * Potato * Water * Sugary Substance (glucose) * Electric mass balance * Kitchen roll * Measuring cylinder Diagram: I have drawn a diagram to show what the experiment will look like. I have used the best equipment available to me to carry out this experiment thoroughly. Fair Test: It is very important to make the experiment a fair test. If it isn't then the results I discover could be incorrect. To make sure it is a fair test I should take special care to make sure I weigh all the potatoes carefully and record their weights correctly. Also, to pay extra attention when weighing the water and glucose solutions out by using a very precise pipette. I will not be able to make all these things exact but I can try and make my measurements as accurate as possible. I should also make sure I use very sensitive scales, which clearly say zero before I place the potato on so as not to get a false reading. Another very important thing to make the experiment fair is to make sure all the potatoes are fully submerged in the solutions so the surface area being affected by osmosis on each potato is equal. Also, it is important to make sure all the potatoes get an equal amount of time in their solutions, but obviously their times will differ slightly but I will try to make the differences as little as possible. I will also try to make the molar concentrations of the solutions as exact as possible to prevent the test from being unfair. ...read more.

Conclusion

By increasing the temperature, this rate of diffusion can be increased and thus, the process of osmosis is faster. This is because, by increasing the temperature, we increase the kinetic energy of the water molecules and thus they diffuse across the semi permeable membrane at a greater speed. Concentration Gradient: The concentration gradient is actually the difference in concentration between the two solutions, separated by the semi permeable membrane. If the concentrated solution is altered so that it has a greater concentration, it will now require more water movement from the dilute solution. Thus, more water molecules must diffuse across the semi permeable membrane. As a result, the process of osmosis is increased as the water molecules diffuse across the membrane faster in order for equalization to occur. When the concentration difference is greater, we say the concentration gradient is steeper. Size of the Molecules: When a molecule is heavier, then it will obviously take a greater deal of time to diffuse across the semi permeable membrane as the molecules speed is decreased. This is also why the solute molecules from a hyper tonic solution do not move into a solution. In cells, the cell membrane is semi permeable. However, in experiments, the membrane may longer act as a sieve and the solute molecules can diffuse across the membrane. However, since the solute molecules attract water molecules, which form clusters around them, this causes the solute molecules to become heavier. Thus, they diffuse more slowly than the free water molecules in the solution. Permeability of the Membrane: In osmosis, the water molecules will move across the semi permeable membrane. This membrane in cells is generally the same size. However, plant cells have the presence of the cell wall, which contributes to the thickness of the cell membrane. Therefore, since the membrane is thicker, the rate of diffusion is greater as the water molecules must move over a greater distance. As a result, the rate of osmosis is decreased. By Arun Joshi ...read more.

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