- Then I will cut 9 pieces of potato
- I will then get 3 different Concentrations of sucrose solution and add 20cm3 to each test tube
- Cut a 4 mm in diameter tuba to 1 cm in length
- Now I will measure the length and mass
- Now leave this for 15 minutes
- Now I will measure the length and mass
Preliminary Results
After we did the Preliminary Test we decided to use 1 cm long 4 mm diameter tubas. We would put them in 25 cm3 sucrose solutions. I don’t have any actual results because the potato tubas shrivelled up in the fridge.
Method
1. I took two average sized ground potatoes and checked that they were both healthy and hard.
2. Using a standard kitchen knife I peeled the potatoes and used a potato tuba to cut 18 equally size tubas
3. Using a scalpel and ruler I cut the potato into lengths of 4mm by 10mm. I had to be very careful whilst cutting the potato as the scalpel is exceptionally sharp. I then had 18 tubas
4. Taking a test tube rack I placed 18 test tubes in it and then labelled them (0.00M, 0.25M, 0.50M, 1.00M, 1.50M, 2.00M)
5. Using a measuring cylinder I measured out 25cm3. I then poured this carefully into each of the 18 test tubes.
6. I then weighed every potato chip on an electronic balance and recorded the weights.
7. I swiftly put 3 potato chips into each test tube and then started my stopwatch. 3 chips were used to create an average which gave me a better set of results and more accurate graphs.
8. Whilst waiting I set out some paper towels with which I was going to dry the tuba.
9. After 15 minutes I drained out the solutions in the sink and placed all the tubas on the paper towel in the order. I wrote on these towels which molar they came from and the test number.
10. I dried each chip with the paper towel and then placed each one on the scales so that I could weigh them.
11. Each potato was measured accurately on the electronic scales and then the weights were recorded.
12. when completing all the concentration I had got 3 results per concentration, I took an average of this result.
13. I then worked out the average % change in mass.
Diagram
Conclusion
This graph shows the line of best fit for the percentage change in mass of the potato tubers over the course of the fifteen minute experiment. The graph is a straight line that slopes upwards and does not go through the origin. Because the line is not very steep, I cannot say there is a strong relationship between the mass and concentration. However, there is a pattern on my graph, and this is, as the concentration of the solution increases, the percentage change in mass increases. The graph shows that the percentage gain and loss in directly proportional to the concentration. The results are quite spread out and are not accurate, so it is hard to come a firm conclusion.
Because I have the equation of the line of best fit I can predict a result, I will try to predict the mass when the molarity is 2.5…
0.0059 * 2.5 + 0.0471
0.06185 = 6.2%
to see if my results are accurate I could try out this experiment using 2.5 molar solution and see how close the actual % is the prediction.
Evaluation
I think this investigation didn’t go very well this may be because at tops we only have a hour at a time to do the experiment this may explain why the some of my results were inaccurate. If I were to do the experiment again I would use more accurate measuring equipment and have at least two hours do the practical. I would do this so I wouldn’t rush the practical and take extra care with measurements. i would also be able to leave the tubers in longer so I could work out the saturations point and also the point of equilibrium, and therefore could find the water potential inside the tissue.
To measure the tubers I think I would use a digital measurer that goes to two decimal places for accuracy and it would go to the same accuracy level as the top pan balance.
I would also increase the amount molar amounts I use, such as 0.25 and 0.75. one explanation for the bad results is when the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time. I were to repeat the experiment I would have possibly found a machine to cut the potato as it would ensure that all potatoes would be the same weight and dimensions. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each tuber on a more accurate scale, e.g. not to 0.00g but to 0.0000g
