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  • Level: GCSE
  • Subject: Science
  • Essay length: 1257 words

To find out at what concentration of sugar there's no osmosis.

Extracts from this essay...

Introduction

Biology Coursework: Osmosis Caroline Snopek Aim: To find out at what concentration of sugar there's no osmosis. Background Knowledge: Osmosis is the movement of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. Semi-permeable membranes are very thin layers of material (cell membranes are semi-permeable) which allow some things to pass through them but prevent other things from passing through, i.e. water. Osmosis is sometimes called a special case of diffusion because the water molecules move from a high to a low concentration of water molecules. In this case, sugar molecules are too big to pass trough the semi-permeable membrane but the water molecules aren't. The water molecules in the high concentration region will want to spread out and the only way is to go trough the semi - permeable membrane. Planning: In this experiments I'll be using potato discs which have a semi-permeable membrane that will allow me investigate the affect of osmosis in different sugar concentrations. Preliminary Results: Concentration Mass before (g)

Middle

:) Using a bore create a cylinder of potato. :) Using a scalper cut this tube into 25 thin discs. :) Separate discs from each other. :) Sort the disc into five sets of five discs and weigh the mass of each set on a top-pan balance. :) Put each set into a labeled test-tube and cover with a different concentrations of sugar solutions. :) Leave the samples for 25 minutes. :) Take potato discs out and gently dry them with a paper towel without squeezing them. :) Re-weight each set. :) Repeat experiment using fresh potato discs. Diagram: Results: Table 1: showing the mass gain/loss and % change in mass. Concentration Mass Before (g) Mass After (g) % Change in mass (moles/Liter) 0.0 (pure water) 0.42 0.5 190.5 0.39 0.46 179.5 0.2 0.44 0.5 136.4 0.48 0.56 166.7 0.4 0.38 0.4 52.6 0.39 0.42 76.9 0.8 0.42 0.4 47.6 0.37 0.35 54.1 1 0.53 0.5 56.6 0.38 0.34 105.3 Analysis: My hypothesis was correct. The results table shows that the higher concentration of sugar solution the less mass gain for the potato discs.

Conclusion

We also did each experiment twice to make sure the results were reliable. However, I do think there are a few things I could of done to make my results more accurate. First of all I could make my increase in concentration constant rather than increases of 0.2, 0.4 and 0.3, which would give me more detailed that would allow me to study the changes in mass bit more closely. It would be useful to also do a few more higher concentrations after 1.0 to see whether the change of mass would continue to increase as it does when the concentration gets lower. I could also have more people in my group so a number of tasks can be carried out at the same time because for example when it comes to removing the potato discs from the solution some groups might stay longer in the solutions than other. Or if some of the potato discs are on the tissue longer than others more water might be absorbed, slightly effecting the results. Also I'd be able to concentrate more on what I was doing instead of rushing to move onto other sets of potato discs so the results we gain are reliable.

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