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The Effect of Glucose Concentration on the Rate of Osmosis

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Introduction

The Effect of Glucose Concentration on the Rate of Osmosis Aims In this investigation I'll be working to know: � How does the concentration of glucose solution affect the rate of osmosis in potato chips? � Why does the concentration of glucose solution affect the rate of osmosis in potato chips? � How does the mass of potato chips changes in different concentration glucose solutions? Introduction The purpose of this investigation is to observe the factors that affect the rate of osmosis in potato chips and investigate the movement of osmosis through the cells of potato. Background information Diffusion is the net movement of particles from a region of high concentration to a region of low concentration until the concentrations are equal. The speed of diffusion depends n the differences between the concentrations to begin with. Osmosis is a special type of diffusion, it occurs across a permeable membrane which allows some particles to diffuse through it and prevent others. Therefore osmosis is the passage of water from a region of high concentration to a region of low concentration through a semi-permeable membrane. The direction and the rate of osmosis depend on the difference in water concentration between the two sides of the membrane and this movement will continue until equilibrium is reached. Cell membranes will allow small molecules like oxygen or water or carbon dioxide or glucose to pass through but they will prevent larger molecules like sucrose or starch or protein to pass through. The tendency of water to move through a partially permeable membrane is described as its water potential and is at a maximum in pure water. As solutes are added the water potential lowers and this means that more concentrated solutions have lower water potentials than more dilute solutions and so the water will have a greater tendency to move from pure water to any aqueous solution and from a more dilute solution to a more concentrated solution. ...read more.

Middle

Then I will work out the average difference in mass and length of each potato chip between before being put in the glucose solution and after being taken out. Then I will repeat the whole experiment exactly the same for another two times to get more precise and reliable results, also if any result does not fit in the pattern I will repeat in order to get as low anomalies as possible. Then I will plot the results in a table and draw two graphs, one for concentration against mass and the other one for concentration against length, before analyzing my results and graphs. Prediction I predict that as the concentration increase the rate of osmosis will increase, and that is because water molecules move from the weaker solution (high concentration) into the stronger solution (lower concentration) until equilibrium is reached. So when the glucose solution is stronger than the cell sap of the potato cells water molecules will move from the potato cells into the glucose solution decreasing the chip's mass, while when the glucose solution is weaker than the cell sap of the potato cells water molecules will move into the potato chip's cells increasing its mass. If potato chip is surrounded by water or a solution more dilute than its contents water will pass into the vacuole by osmosis and the vacuole will expand and press outwards on the cytoplasm and cell wall, so there comes a time when the inflow of water is resisted by the un-stretchable cell wall. If the potato chip's cell vacuole is pushing out on the cell wall it is said to be turgid and the vacuole is exerting turgor pressure on the cell wall. If all the cells in the chip are turgid it will be firm and longer and if the vacuoles lose water the cells will lose their turgor and become flaccid and shorter. ...read more.

Conclusion

the potato chips or between the cells in the potato chips, also the reason might be a misreading of scale or a mistake by taking the measurements of the glucose solution and the diluting water. Another possible reason could be the affect of temperature on the rate of osmosis, because as we know temperature affects the rate of osmosis by speeding up the molecules which will decrease the time needed for a certain length or mass to be reached. However there are still some experimental errors which can be identified by looking on the graphs. Graph 2 is more precise and accurate than graph one, as graph 2 have nearly a straight line and I think this is because in the first method (mass) it was very hard to maintain accuracy due to excess water on the potato chip and between its cells, while in the second method (length) it was easier to obtain more precise and accurate results because the change was obvious and can be measured easily by ruler. According to my evidences my conclusion, which is that as the concentration increases the rate of osmosis increase and as the concentration gets higher the potato chips will lose more mass and length, is right and a good prove is that I have repeated the experiment three times; also I have repeated the anomalies which did not fit in pattern with the rest of results in order to get the reliable and precise results. And by repeating the anomalies I have got a very precise and accurate mean that helped me to plot precise points in my graphs. Also I wished to extend it more and to see how changing other factors such as the temperature and surface area can change the rate of osmosis, also I wanted to experiment how concentration can affect the rate of osmosis of apple and then compare the thickness of the potato's cell wall and the apple's cell wall. But unfortunately I did not have enough time. ...read more.

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