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Investigating the effect of changing the concentration of a glucose solution on osmosis in potatoes.

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Introduction

Investigating the effect of changing the concentration of a glucose solution on osmosis in potatoes. I am going to investigate how changing the concentration of a glucose solution affects the rate of osmosis in a potato. I will set up 6 different tubes with varying concentrations: 0M, 0.25M, 0.5M, 0.75M, 1M and 1.25M. I will put the glucose solution into a test tube with pieces of potato 2cm long, I will record the mass of the potato before and after to decide whether or to what degree the concentration of glucose affects osmosis. To do this I will leave the pieces of potato in the varying glucose solution for 15 minutes, weight them afterwards, and record the difference in mass and see what I can decide from my results and whether it agrees with my prediction. The only variable I will change in this investigation will be the concentration of the glucose. I will keep the amount of liquid, the size of potato and the length of time the potato is in the solution the same. To make sure this is a fair test I will ensure that only 1 variable is changed. I predict that as the concentration of the glucose solution increases, the mass of the potato will decrease. ...read more.

Middle

It also proved my theory that if water is put into a test tube with a piece of potato, then the water would transfer from the potato. I then set up 4 more test tubes with different concentrations of glucose and pieces of potato, and collected the following results: Concentration of glucose (M) Initial weight (g) Weight after (g) Difference (g) Difference (%) 0.25 0.70 0.69 0.01 1.43 0.5 0.72 0.69 0.03 4.16 0.75 0.73 0.69 0.04 5.48 1 0.72 0.65 0.07 9.72 From these results I can see that as well as it proving my prediction it shows that my method and measurements were suitable. Plan Apparatus * * Potato borer and stick * 6 test tubes * Glucose solution * Water solution * Test tube holder * Potato * Scalpel * White tile * Ruler * Balance * Labels * Stop Watch 1. Collect a potato and us the potato borer to get 6 pieces of potato 2cm long. To get the potato to the right size, measure using a ruler and cut using a scalpel on a white tile. 2. Collect test tube holder and put pieces of potato inside. Stick a label to each tube. Take out each piece of potato, measure the mass, and record in exercise book and number it on the results table, then label the tube with the same number and repeat the process with the other tubes. ...read more.

Conclusion

There could be a number of possible reasons for this, human error for one. I could have misread one or more of the results that gave me the averages and then the percentages, leaving me with an overall inaccurate percentage. Another possible error being the balance might not have been set to zero, or another problem with the balance, again causing inaccurate weighing either before or after the osmosis took place, leaving me with an inaccurate percentage. Even though this investigation provided me with overall clear results, there are ways I could improve and extend the method. To make it more accurate, I could make sure that as well as the potato being the same length, they would be exactly the same mass, and also the same surface area. I could devise a way of estimating the surface area to ensure that the experiment is in fact reliable and accurate. I could also extend this investigation. Firstly, I could leave the potato in the solutions for a much longer span of time, perhaps even 24 hours, so the results would be far clearer. I could also extend the range of the subject beyond potatoes to other vegetables, to prove osmosis is not limited to potatoes, likewise an investigation could be made into what happens if animal cells are placed in water and other solutions. ...read more.

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