- We need to use the same weighing scales to obtain the mass because scales can also be different, some may have different measurements than others or weigh objects differently.
- The volumes of the sucrose solution definately need to be kept the same. This is the obvious one because if the solution volumes were different, the experiment would be unreliable as there is a set concentration to a given amount of solution. This would effect the experiment as the potato would absorb the incorrect amount of solution each time. Not only that but I believe the potato should be fully submerged each time as then it would have total contact with the solution.
- The same stopwatch must be used for each experiment as some watches may differ leaving extra or less time for some chips.
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 sharp knife, which could injure someone if it´s not handled properly. We will also be careful that the solutions don't get into our bodies internally, just in case, because we are not fully aware of the damage it could do to us. But other than that, there weren't any bigger matters to be cautious of.
Method
First I will have to get the pieces of potatoes ready, I will cut each piece into 5cm chips. I will then weigh each chip individually for my 'before' part of the experiment and have them ready to go into the boiling tubes. I will have 6 sets because we will have to test the potatoes in 6 different types of solutions; 0.2, 0.4, 0.6, 0.8, 1.0 molar solutions of sucrose. I will then put 3 potato chips into each one of the 6 boiling tubes and set the clock running for 10 minutes. After 10 minutes, we will take all of the potatoes out of the test tube, so that the actual osmosis action stops, and we will put the potatoes onto one piece of dry towel, in their own groups. We will dry them with the tissue paper, in sets of 3, and weigh and measure the potatoes taking in the average reading of the 3 pieces. It might be necessary that we repeat the experiment so we can make sure all our results are similar and so that we will be able to take the average of the 3 chips, this makes sure that we get accurate results. Repeating the experiment is important, because we will be able to obtain reliable results, and look for any anomalous results. Not to mention that we will take the fair testing into account.
Prediction
For this prediction I will use my knowledge of Osmosis. My predictions are that molars 0M - 0.4M will be very dilute, more so 0M which means that they will have a higher water potential. I know for this that the solutions of these molars will be longer and heavier in mass.
The molarity of 0.6M - 1M will be quite concentrated, especially 1M which I predict will be extremely concentrated therefore meaning that these molars will have a lower water potential. I also know for this that the solutions of these molars will be shorter and lighter in mass. The halfway molar (0.5M) should determine that the results remain similar to what they were at the start because written down the amount of sucrose solution going in remains the same coming out. I predict that the results for the halfway molars 0.5M will be close to what they were at the start but not the same.
Obtaining evidence
I am going to outline the experiment again first. I put 3 potato chips to each boiling tube, there were 6 tubes in total. Each one had a different concentration of a sucrose solution and the aim of the experiment was to find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose solution as said.
After the experiment, I had to dry the potatoes first, so that the water outside the tissue of the potatoes would not alter the weight of what it is supposed to be. I quickly took all of them out, and put them onto a piece of tissue paper, into their own groups as stated. Upon obtaining the results, I reset the balance of the scales so that it would read zero with the plate that the chips would be placed upon on top of it. Mainly because if I had weighed the potato chips with the plate, the scales would not have acounted for the plate and I would have had to subtract the weight of the plate away each time.
Table Of Results
Having done the experiment following my plan, I am goingto work out my mass and length tables. First of all I am going to write down the 'before' and 'after' results of the mass:
0M = Before - 1.46g 0.2M = Before - 2.32g 0.4M = Before - 1.35g
After - 1.70g After - 2.46g After - 1.42g
0.6M = Before - 2.00g 0.8M = Before - 1.69g 1M = Before - 1.46g
After - 1.94g After - 1.53g After - 1.88g
Here we can see the 1M result is anomalous and must be wrong as it is totally different to the others.
Percentage increase/decrease for mass
0M = 0.24 ÷ 1.70 x 100 = 14% increase
0.2M = 0.14 ÷ 2.46 x 100 = 6% increase
0.4M = 0.07 ÷ 1.42 x 100 = 5% increase
0.6M = 0.06 ÷ 1.96 x 100 = 3% decrease
0.8M = 0.16 ÷ 1.53 x 100 = 10% decrease
1M = 0.42 ÷ 1.88 x 100 = 22% increase
Percentage increase/decrease for length
0M = 0.4 ÷ 5.4 x 100 = 7% increase
0.2M = 0.2 ÷ 5.2 x 100 = 4% increase
0.4M = 0.1 ÷ 5.1 x 100 = 2% increase
0.6M = -0.1 ÷ 4.9 x 100 = -2% decrease
0.8M = -0.2 ÷ 4.8 x 100 = -4% decrease
1M = 0.7 ÷ 5.7 x 100 = 12% increase
Just by looking at these results I can see there is a distinct pattern apart from the 1M result which most definately has to be considered anomalous. Without including our 1M result, the experiment has followed my predictions. Osmosis took place throughout this, and as I mentioned before, 0M - 0.4M were very dilute and had a higher water potential, therefore leaving the chips heavier in mass and longer in length. It was the same for the molars of 0.6M- 1M as my prediction for them came true, all apart from the last one however. They had a lower water potential therefore they were shorter in length and lighter in mass. This is true for 0.6M and 0.8M but 1M was longer and heavier as opposed to shorter and lighter.
Graph Analysis
I have plotted my graph and drawn the line of best fit for it. I notice that it fits perfectly apart from the 1M result obviously which is dramatically different from the rest and as said before is most definately considered the anomalous result of this experiment.
(Graph)
Conclusion
I think that this investigation was successful. Successful meaning my results collaborated my predictions. The potato cells, working to stay alive, took in (absorbed) or gave out the water depending on the concentration of the tissue and the concentration of the solution it is surrounded in. The results turned out well giving exception to the last one, the 1M result which was decided as the anomalous result of this experiment. It was the only reading that appeared to be out of line. The weights of the potato chips before the experiment took place ranged between 1.35g - 2.32g. This indicates that the potato chips were cut reasonably well but were accurate enough to provide us with reliable results. The graph and the results show us that Osmosis actually took place in this experiment and that as the molars increased, the percentage of the weight difference decreased. The results more or less backed up my predictions which suggests that the experiment was an achievement.
Evaluation
I think that we followed the plan correctly and that we gained accurate and reliable enough results to conclude this experiment. The final results obtained were quite reliable and there was a distinguished pattern between them, except the last one (1M) which can be made accurate through trial and improvement. There are many things we can do to improve the experiment, some being:
- Weigh each chip individually to obtain even more accurate results
- Use a Burette to measure the sucrose solution more acurately
- Done one test at a time so that we could reduce the time difference upon moving the chip from the boiling tube to the weighing scales as between this we have to dry the potato chips just enough then weigh them accurately. When we are doing this for one set, writing down the results at the same time, while the other 5 sets are being sufficiently dried, the potato tissue is going to vary for all chips. By doing this we would be concentrating individually on each set of chips rather than trying to finish them all as quickly as possible due to limited lesson time. Experimenting with one set at a time would also lead us to better results as the Osmosis action would have the time to reach its full potential hence indicating how much water can be transferred for each solution.
- If more people were in a group, they could be assigned different tasks and would be able to share the workload.
- Using a wider range of molar sugar sucrose solutions would help us obtain better and accurate results as we would have a wider range and would be able to check our answers against others.
Finally repeating the experiment using a 'trial and improvement' theory would lead to accurate results, especially if done 3 times as it would be clear which set of results were wrong when checked against eachother.
In conclusion I think that with the equipment used in this procedure, I think that the experiment turned out to be relatively successful and I am pleased with the results obtained, even the anomalous one as I know now what I can do to improve it.
