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Potato chips experiment

Extracts from this document...

Introduction

Investigate the effects of different concentrations of salt solution on potato cells Introduction Osmosis is the way in which many living things take up water (source: GCSE Biology for You). During osmosis, water moves from a dilute solution to a more concentrated solution through a semi-permeable membrane. This membrane allows water molecules to pass through easily, but does not allow solute molecules to do this. The movement of these water molecules gradually dilutes the solution that had the higher concentration until they are equal, or as close to equal as possible. The following is a practical example that effectively demonstrates osmosis. Example A Example B % change in mass Mass at start (g) 16.7 20.6 Mass at end (g) 11.8 25.2 From this example, we can see that example A reduced its weight by 4.9g, meaning that water molecules moved from the pure water into the salt solution through osmosis. Similarly, example B gained 4.6g, meaning that water molecules moved through the semi-permeable membrane from the lower concentration of salt solution to the higher concentration through osmosis. Preliminary work Apparatus ? 3 galley pots ? 60 ml saturated salt solution ? 60 ml distilled water ? potato chips ? knife ? balance (accurate to 1d.p.) ? 50 ml measuring cylinder (accurate to 1ml) ? stopclock (accurate to 1d.p.) Variables ? Size of potato chip ? Time left ? Surface area of potato chips ? Age of potatoes ? Concentrations of salt solution ? ...read more.

Middle

Using a syringe would be a more accurate measurement and would therefore give me more accuracy in my results. It would also make the test fairer. Chosen measurements and concentrations I have chosen to change the concentrations that the potato chips are and measure the change in mass because I believe that this will most effectively show me the affects of osmosis on plant cells. I have chosen to use 40ml of salt solution and water in each pot as in my preliminary work I found that this is enough to cover the potato chips fully, and the concentrations are not difficult to work out and measure. I will be using salt concentrations of 0, 10, 20, 30, 40, 50, 70 and 100%. I have chosen to use these as the concentration of salt in the potato cells will be below 50% as potatoes are not salty foods. My preliminary work also showed that the concentration of salt in the cells was below 50%, as at this concentration the potato chips decreased in mass by 8.88%. Safety To ensure that my experiment is safe, I will wear goggles throughout and tie my hair up. I will also wash my hands before and after the experiment. Fair test I will ensure as far as possible that my experiment is a fair test by ensuring that I only use one variable. I will keep the temperature that the pots are kept in the same; they will be left in the same area of the room. ...read more.

Conclusion

The surface areas were also not exactly the same. This would only affect my results very slightly, if at all, but is something that I could possibly improve in future by measuring the dimensions of the potato chips, or using a potato cutter that cuts the chips equally. It was also quite hard to dry and reweigh the potatoes at the same time, so there was around a two-minute gap between the first re-weighing and the last. Again, this may not have affected my results very much, or at all, but in future I could use more balances and more people so that all the chips are removed from the solutions, dried and re-weighed simultaneously. This would improve the accuracy of my results very slightly. I felt that the balance I used was accurate enough, and that the quantities were measured accurately. However in future I could improve this accuracy by using balances accurate to three decimal places and a digital syringe to ensure that my quantities are exact. Therefore, my results are reliable and allow me to draw an accurate and reliable conclusion. In the future, I could extend my investigation by using different concentrations of salt solution, for example ranging from 0-10% salt solution. I could also use more concentrations in my experiment, which would give me more results. This would then also give me a more accurate line of best fit, and give me a more accurate measure of the salt concentration inside the potato cells. Therefore, the reliability and accuracy of my results and conclusions would be improved. ...read more.

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