Getting and experimenting with the exact measurements of molars and water is vital to this task. If the volume of one solution in a test tube is higher or lower than another, will affect the pattern of results later on.
We will also make sure that each potato is fully covered by each of the 5 different kinds of solutions. This is because, is the potato isn’t covered up by the solutions, the effect of osmosis will not occur to the fullest, giving anomalous results.
Factors such as a dirty test tube, and a slightly cracked measuring cylinder could still affect the results, and therefore we will use the best equipment available to us.
Safety: Safety is an important aspect in every experiment, even if the experiment seems to be very harmless. And that is why we take this into consideration, no matter what.
We will be using a very sharp knife, which could injure someone if it’s not handled properly, and we have to be careful when handling the burette as it is made out of class and very fragile.
Apparatus: glucose (varying molars from 0-2),
potato,
ceramic tile,
scalpel,
burette,
test tubes,
test tube holder,
glass beaker
Method: I believe this task is very simple and it should be very easy to carry out the experiment. The investigation is very straightforward.
First I will have to get the pieces of potatoes ready. I will push the cork borer through the potato, cutting it into long cylinders with a diameter of 6mm. And then I will cut the potatoes into cylinders of 40mm, and weigh 3 sets of 5 potato cylinders. I will have 3 sets so at the end I can take an average and I will be able to spot any anomalies. I will have 3 test tubes of each different molar of glucose mixed with water, which shall be 0.0, 0.5, 1.0, 1.5, and 2.0. This works out as 20ml water, 15ml water + 5ml glucose, 10ml water + 10ml glucose, 5ml water + 15ml glucose, and 20ml glucose respectively.
I will weigh each set and have them ready for us to put into the test tube.
Then we will put the 3 sets of 5 potatoes in the 15 test tubes at the same time, and then leave them over night.
The next day, we will take all of the potatoes out of the test tube, so that the actual osmosis action stops, and we will dab the potato chips dry on sheets of dry paper towel, keeping record of which one is which. We will then weigh the potatoes taking in the average reading of the 3 sets.
Results:
Analysis: My graph has a negative gradient and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain/loss in mass and morality are not directly proportional. However, there is a pattern on my graph, and this is, as the concentration of the glucose solution increases, the percentage change in mass decreases. The gradient does change in my graph. It gets less steep as 'x' gets bigger. This is because the potato chip is becoming as flaccid as it possibly can, and so the change in mass of each morality are becoming closer and closer together. All of my results lie close to my best-fit curve. This shows that my results are fairly reliable. My graph fits in with my prediction of the experiment graph.
The average distilled water gains in mass. This means that osmosis takes place and that the water moves from the beaker into the potato. The matches my initial predictions. The point where the line crosses the x-axis is the isotonic point. This is where no osmosis is taking place, i.e. no water is moving in or out of the potato. The first point 0 molar gained mass the next point, 0.5 molar looses mass. This shows that the water potential of the glucose solution in the beaker is stronger than that of the potato chip. All the rest of the results loss mass. This shows that the water potential in the beaker is less than that of the potato chip. Also that the potato is trying to make the water potential of the fluid on both sides of the semi permeable membrane the same, (osmosis from the potato to the glucose solution, from a higher water potential to a lower one). This pattern carries on through the graph, and even more mass is loss, as more water moves out of the potato. My results tally with my initial predictions. These were that osmosis would take place, and as the water potential decreases, the percentage change in mass will decrease.
There were two errors in my results, which I have highlighted in red. As both of these were above the corresponding results gained in the other two experiments I believe it is due to the fact that I failed to adequately remove all excess water on the potato chips. I left both of these erroneous results out of my average graph.
Evaluation: We followed the plan correctly, I believe we gained accurate and sufficient enough results to conclude the experiment, and to prove our predictions.
My final results were very reliable, due to the precautions I took to make this a fair test.
To make this experiment better, I believe that when we have to move the potato from the test tube to the balance we should try and do this as quickly as possible. We also have to dry the potatoes just enough, and then put it on the balance. When we are doing this for one set, writing down the results at the same time, while the other 3 sets are on the tissue paper, the water outside the potato tissue is going to vary for all. Therefore, we would be able to concentrate more on one of the sets, instead of trying to finish all of them as quickly as we can.
Using more types of molar sucrose solutions would have helped us obtain better results, and more accurate results, and given us a better idea of where the isotonic point was, so that we can make sure the results are totally correct.
Experimenting with one set for a longer period of time, for each set, would lead us to better results, because the osmosis action would reach its maximum capability, and therefore tell us how much water could be transferred for each solution.
Even though we didn’t use these experimental plans, we still got results which were correct, according to my prediction. Overall, given the apparatus that we got to carry out the test, I think this experiment turned out to be very successful, and I’m very please with my results.
