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Osmosis - Investigation

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Introduction

Aim; The aim of this investigation is to conduct a fair and simple test to investigate if, when the surface area of a core of potato is altered, will this affect the mass of the same core? Osmosis- Scientific theory; Osmosis is a biological procedure, during which a substance is transferred from one solution to another through a semipermeable membrane. In solutions containing sugar, the water is able to pass through this membrane but the sugar is not. This is how osmosis works: Prediction; I think that in the experiment, the smaller cores of potato will increase in surface area and mass the most. I think this because if they are smaller, they have a more concentrated area to begin with and the water will replace all the starch inside due to the change in the concentration gradient. If there is a concentrated solution, starch, inside the potato and a dilute solution outside it, water, then they will naturally be changing places on the concentration gradient. Fair testing; As with all experiments, I will aim to keep this one as fair as possible by not changing any possible variables. The first variable will be the volume of distilled water that each potato core is to be placed in. ...read more.

Middle

Using a measuring cylinder, measure out 50ml of distilled water into each test tube containing the potato cores. The tubes and cores now have to be left for 10 minute, timed with a clock or stopwatch. When ten minutes has passed, the cores are removed from their solutions and carefully dried off. They then have to be replaced on the electronic balance and he finishing masses taken and recorded. Using the start and end masses, the percentage increase or decrease of the surface area has to be calculated. To get some more sets of results for comparison, the experiment should be repeated up to five times after the initial time. The results; Preliminary test; Before being placed in the distilled water: Size of potato core (cm) Mass of potato core (grams) 5 1.65 4.5 1.42 2.25 0.93 1.125 0.45 0.5 0.18 After 10 minutes in the distilled water; Size of potato core (cm) Mass of potato core (grams) Percentage change 5 1.75 6% growth 4.5 1.46 2.8% growth 2.25 0.98 5.4% growth 1.125 0.47 4.4% growth 0.5 0.20 11.1% growth Quick reflection; as you can see, the smaller cores of potato have had the greatest increase in mass, as I said would happen in my prediction First repetition: Before being placed in distilled water: Size of potato core (cm) ...read more.

Conclusion

This is because there aren't any anomalous results as before and the differences aren't too erratic or seemingly stupid. Evaluation: Overall, I think that this investigation was conducted well. The basic aim of the investigation was carried out and several repetitions provided me with reliable evidence to use. Despite there being a few anomalous results, there were enough good results to use to draw a conclusion from it all. I think that I carried out the experiments quite well, sticking to the outlines in the 'fair testing' section of this write up. The only problem that I can think of with this investigation was finding somewhere to position it away from direct light, because there were a lot of windows nearby and the sunlight was quite intense, this may have caused evaporation on some of the experiments and so causing the anomalous results. Conclusion: As stated in my prediction, the smaller cores have encountered the most percentage growth because of the concentration gradients of the starch and the water. The results from the tables were placed onto the graphs and if a pattern seems to be emerging then it would be possible to estimate results for different sized cores than I have used. The results on the graph are just as accurate as the ones in the table because they are the same so there is no room for any criticism there. Osmosis investigation - Biology coursework ...read more.

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