Prediction:
I predict that the weaker the solution is, the more solution the potato will absorb and the stronger the sugar solution the more water the potato will lose. Therefore, the weight of the potato at the end of the experiment will increase most in distilled water and decrease most in the strongest sugar solution.
I also believe that the apperance of the sample s that take in water eill be firmer and feel more rigid and the opposite for the samples that may lose water they shall become flaccid and feel very soft to the touch.
Apparatus:
Potato
- Scalpel
- Tweezers
- Test tube rack
- 6 test tubes
- Cork borer
- Ruler
- Mat
- Scales
- Sucrose solutions(in moles 10ml per tube)
0.2
0.4
0.6
0.8
1
Method:
1) Using the cork borer take six samples of potato from the same potato. Then using the scalpel cut the pieces of potato so they are twenty millimetres long. Remember to weigh the potato pieces and record their weight in a table.
2) Take six test tubes and place them in a rack, then add the different sugar solutions. These are sugar solutions, 10%, 20%, 30%, 40% and 50% and one test tube filled with water.
3) Place the potato pieces in the test tubes; make sure they are covered with solution. Leave them there for thirty minutes.
4) Take the potato pieces out carefully and measure their length and weight, record this in your table and repeat twice more.
Key Factor:
The key factor in my experiment is the concentration of the sucrose sulution ranging from 10% to 50% I also used distilled water. I think that this is a suitable range of concentrations. The factors that I will control are the points in my fair test.
Scientific reasoning
When a substance such as sugar dissolves in water, the sugar molecules attract some of the water molecules and stop them moving freely. This, in effect, reduces the concentration of water molecules. In Fig. 11 the sugar molecules on the right have captured half the water molecules. There are more free water molecules on the left of the membrane than on the right, so water will diffuse more rapidly from left to right across the membrane than from right to left.
The partially permeable membrane does not act like a sieve, in this case. The sugar molecules can diffuse from right to left but, because they are bigger and surrounded by a cloud of water molecules, they diffuse more slowly than the water.
Artificial partially permeable membranes are made from cellulose acetate in sheets or tubes and used for dialysis rather than for osmosis. The pore size can be adjusted during manufacture so that large molecules cannot get through at all.
The cell membrane behaves like a partially permeable membrane. The partial permeability may depend on pores in the cell membrane hut the processes involved are far more complicated than in an artificial membrane and depend on the structure of the membrane and on living processes in the cytoplasm. The cell membrane contains lipids and proteins.
Anything, which denatures proteins, e.g. heat, also destroys the structure and the partially permeable properties of a cell membrane. If this happens, the cell will die as essential substances diffuse out of the cell and harmful chemicals diffuse in.
Fair test:
To make this experiment a fair test I will use the same…
Length potatoes- so that there is the same length of potato for osmosis to take place in.
Room temperature- so that this doesn't affect the rate of reaction.
Size cork borer- so that the size of the potato doesn't vary.
Amount of sugar water- so that the potato pieces have no more or less sugar solution to absorb.
Amount of time potatoes are left in sugar solution. - so that I can record accurate results.
I will also put corks in the top so that the solujtion cannot evaperate.
Safety:
Safety is an important aspect in every experiment, even if the experiment seems to be very harmless. This is why I'll be taking this into consideration. I will be using a very sharp knife, which could injure someone if not handled properly. I will also be very careful that the solutions don't get into our bodies internally, because we are not fully aware of the damage it could do to us.
Results:
Set 1
Set 2
Set 3
Conclusion
The evidence obtained from this investigation supports the prediction I made. It also shows that the potato cells increase mass in solutions with a high water concentration and decrease in mass in solutions with a low water concentration. I have been able to identify a pattern in my results, in the difference in weight.
In this experiment, I believe that I have collected enough data to support my hypothesis. This investigation was, I think, successful. Successful meaning my results collaborated my predictions. The potato cells, working to stay alive, took in, or gave out the water depending on the concentration of the tissue and the concentration of the solution it is surrounded in. I have been able to record sufficient results by repeating the experiment three times.
Evaluation
We followed the plan correctly, I believe we gained accurate and sufficient enough results to conclude the experiment, and to prove our prediction.
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 we could have done one test at a time, so that we can reduce the time difference, when we have to move the potato from the test tube to the balance. Between this, we 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 5 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.
We also could have got more people to do the experiment with us, so that we can organize the tasks, and we would be able to divide the tasks.
Using more types of molar sucrose solutions would have helped us obtain better results, and more accurate results, 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.
Repeating the same tasks many other times wouldn’t have been very useful, since we had already done the result 3 times, and ALL the results were reliable.
Even though we didn?t use these experimental plans, we still got results which were correct, according to my hypothesis, and backed up my predictions.
But overall, given the apparatus that we got to carry out the test, I think this experiment turned out to be very successful, and Im very please with my results.There is a positive correlation .