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To investigate the effect of different concentration of sucrose on osmosis in potato chips

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Introduction

Biology practical coursework Aim of investigation: To investigate the effect of different concentration of sucrose on osmosis in potato chips. Independent variables: The independent variable is the concentration of sucrose solution. How will the independent variables be controlled (Details of dilutions)? Molarity of solution/M Amount of sucrose solution/cm� Amount of water/cm� 1.0 10 0 0.8 8 2 0.6 6 4 0.4 4 6 0.2 2 8 0.0 0 10 Dependant variable The dependant variable is the size of the potato chip (mass and length) How we will measure the dependant variables * Length ?The length will be measured using simply a ruler to nearest mm * Mass ?The mass will be measured on a balance to nearest 0.5g. The potato chips will be blotted first to remove excess sucrose solution outside of the chip, to obtain more accurate results, as the excess mass of any solution will mean the chip weighs slightly more than it would normally without excess solution. Variables and why they need to be controlled Temperature- The temperature will have to be controlled because at a higher temperature molecules will move faster (possibly if we put it on the window sill due to the extra heat from the sun) this will mean � more kinetic energy. And eventually means osmosis is more likely to happen at a quicker rate since the particles are moving quicker. Each particle since it is moving faster is likely to hit the partially permeable membrane at a quicker rate, and hence go through it, in the end increasing the rate of osmosis. Volume of sucrose solution- Not enough sucrose solution therefore won't cover chip - Measure solution. The volume of water molecules will affect the amount of osmosis taking place. Surface area of chip- The surface area of the chip will have to be controlled by cutting the chips accurately using chipper and ruler. This is because surface area affects the rate of osmosis, because the higher the surface area the more water molecules can pass through the semi permeable membrane, and also the higher the surface area, the quicker the rate of osmosis. ...read more.

Middle

Water moves into the cells of the chips because of osmosis because there is a higher concentration of water outside the chip than inside and the water moves from a (high) to (low) concentration of water through the fully permeable cell walls of the potato and the partially permeable cell membrane. This is true for the concentrations of 0.0M and 0.25M since there is a higher concentration of water outside the potato chips in the 0.0M and 0.25M solutions than inside. From this we notice that the cells gain mass and the cells become turgid and swollen up. For 0.5M, 0.75M and 1.0M of concentration, there is a higher concentration of water inside the cell than outside the cell. The chips in these concentrations lose water through osmosis. The water moves from a high concentration of water (more dilute solution) from inside the cells to a low concentration of water outside the cells (more concentrated solution) into the 0.5, 0.75 and 1.0M solutions through the partially permeable cell membrane and the fully permeable cell wall. From the graph, which demonstrates the results table in a pictorial way, we can tell when and where the concentrations of the solutions affect the % change in water. From the graph we can tell that osmosis occurs with the water moving from a higher concentration of water from the solutions to a lower concentration of water inside the cells of the potato chip. This is from the 0.0M and 0.25M, but we can tell reading from the graph that up to about 0.28M the same would occur. At roughly 0.29M there would be no percentage change in mass, as it is where the line passes the y axis (% change in mass). We can also deduce that from a concentration of 0.29M or more the potato chips lose water through osmosis, as it is shown by the negative percentage change in mass. ...read more.

Conclusion

The peeling of the potato should be regular too, so the exposed surface of the chips is regular, and any osmosis occurring isn't affected by the skin. * Finally a lot more repeats could be done as opposed to just 2 repeats. This would obtain a lot more data for each and every concentration, and allow for a more accurate average mass change, since a larger group of mass changes is being averaged. Although this would be very time consuming, it would however enable us to check for any mistakes made as opposed to if we just did 2 repeats. Confidence in data Since we used 5 concentrations and did 3 runs for each one I would say that we had enough data to say whether it was a good experiment or bad one. Overall I would say it was pretty successful and it followed my prediction, apart from one anomalous result which didn't follow the general trend. Could our results enable us to work out the concentration of water inside the potato chip? Yes, from the graph we can say that the point at which the line crosses the X axis. However this is just relying on where assumed and the actual results. We could not say for certain very accurately whether we would be able to or not. Further possibilities Some further possibilities could include for example: * I could do more concentrations within our range. * Also I could use salt solution instead of sugar solutions * We could try investigating on different sized potato chips * We could try measuring length of the potatoes and time too, instead of just leaving for a day. * We could try using higher concentrations, and so we get different graphs Acknowledgements The images used for the apparatus were obtained by searching on google images (http://images.google.co.uk/imghp?ie=UTF-8&oe=UTF-8&hl=en&tab=wi&q=). The image of the balance was obtained from 'crocodile clips chemistry.' Finally the other pictures (picture of two beakers, and the picture of test tube) were made by me using Microsoft paint. ...read more.

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