but not as much as the 1M sugar solution because it is not as concentrated,
for the same reason as above.
0.6molar- This is one of the hardest to predict. I think that the potato chips in this
solution will stay about the same length and mass as the sugar solution is about the same
concentration as that inside the potato.
0.4 molar- This is also a hard result to predict, but, I think that the potato chips in the
0.4M sugar solution will stay about the same length and mass because the concentration
of the sugar solution is about the same as that inside the potato.
0.2 molar- The potato chips in the 0.2M sugar solution will increase in length and mass because
the sugar solution will be more dilute that the solution inside the potato
causing water to move into the potato through osmosis and the potato to
grow in length and mass and the cells inside the potato to become turgid.
Distilled Water- The potato chips in distilled water should grow in length and should
have a higher mass because there should be more water outside the
potato chips than inside, therefore, water should move into the potato
through osmosis causing the potato to grow in as its cells
become turgid as this happened in the preliminary experiment 1.
Variables: the only variable in this experiment is the concentration of the sugar solutions. I must make sure that:
- the potato chips are the same length and mass otherwise; I will not be able to compare the affects of the different sugar solutions.
- I have the same amount of sugar solution otherwise, my results will not be accurate as I have more sugar solution, then osmosis may occur more than I had expected and my results will not be accurate.
- I put the solutions containing the potato chips in the same place so that they will have the same temperature as if the temperature was higher in some then osmosis would occur more quickly and more osmosis would occur than expected.
- I cover the test tubes with cling film to prevent evaporation as if the solutions evaporate then that would have the same consequences as having different amounts of sugar solutions.
- I use the same size test tubes, as otherwise the potato chips will be covered by different amounts of solution, which means that osmosis may not occur properly.
- I leave them all for the same amount of time as I leave some longer then the molecules will have more time to travel through osmosis therefore, more osmosis will occur making my results inaccurate.
- I use the same cork borer, as then all the potatoes will have the same diameter making my results more accurate.
- I measure the potato chips mass as well as length to make my results more accurate.
Apparatus:
- 6 test tubes (of equal size)- to hold the potato chips and sugar solutions, they should be of equal sizes to make the experiments fair.
- 6 potato chips of equal length and mass x2 (6 each of 2 sizes)- to carry out the experiments on, then to repeat the experiment so that I can obtain accurate results. They are the same length and mass to make it a fair test.
- The different sugar solutions- to carry out the experiment:
1.0 molar sugar solution
0.8 molar sugar solution
0.6 molar sugar solution
0.4 molar sugar solution
0.2 molar sugar solution
Distilled water
- 6 measuring cylinders- one for each sugar solution to make sure that they are all of the same capacity to make it a fair test and to stop them getting contaminated.
- A cork borer- to cut the potato chips and make sure that they are all the same diameter.
- Ceramic tile- to prevent the cork borer from cutting into the table and to keep the potato chips on to stop them from getting contaminated.
- A potato- to cut the chips out of, I will use the same potato for all the chips so that the amount of water it contains will be the same in all the chips at the beginning of the experiment.
- A knife- to cut off the skin of the potato and to cut the potato chips to size.
Method: I will set up the apparatus as shown in the diagram. I will cut the potato using the cork borer on the ceramic tile and cut off the skin. I will then measure six potato chips with 20mm lengths and six with 10mm lengths using the same potato to cut all of them. I will then measure the masses of all the potato chips to make sure they are the same. I will then measure out all of the solutions using different measuring cylinders for each so I do not contaminate them using the same amount of solution in each and pour them one each into my equal sized test tubes before placing the potato chips inside the test tubes one of each length in each. I will them place them in a test tube rack. I will then coven the test tubes with clung film to prevent evaporation before leaving them in the same place for 24 hours. I will then record the results at the same time to prevent any of the chips drying out and therefore, changing the reliability of my results. I will put cling film on the top because when I did the same experiment with 3 solutions, some of the solutions evaporated, I am using two potato chips in each solution so that I can find an average percentage change as my results in the experiment with the three solutions were not very accurate.
Results:
I did the experiment safely, as planned and measured the length and mass of the potato chips making sure to clean up any spilt solution. I have recorded my results into the table below and calculated the percentage change.
A Table to show the % change in Length and Mass of Potato Tuber Cells after they have been placed into different solutions
Below, I have entered my results into two graphs, one showing the percentage change in length, the other showing the percentage change in mass. I have entered them into graphs so that the results are easier to understand, trends are easier to identify and to identify the range of the results.
To work out the average, I added both lengths together and divided by two.
The calculation for the % change is:
% Change in length = average final length-original length X 100
Original length
% Change in mass = average final mass – original mass X 100
Original mass
Graphs:
A graph to show the average % change in length in potato chips in different sugar solutions
A graph to show the average change in mass in potato chips in different sugar solutions
A graph to show the average % change in mass in potato chips in different sugar solutions
Blah
Blah
Blah
Blah
Anomalous Results: (circled on graphs)
Distilled Water: increased more in % in both length and mass than allowed by my line
of best fit, this may be because the potato was drier than the others
when it was put into the test tube causing more osmosis to occur and
more water to enter the potato through osmosis.
0.2 molar sugar solution: this increased in length more than my pine of best fit
allowed, this may have been because it had been let to dry
more than the others before it was placed into the test tube.
0.6 molar: the length increased by more than my line of best fit allowed. This may
have been because it ad been left to dry for longer than the others, however,
the mass increased by far more than I had expected, this may have been
because the potato chip contained more water than the others. The reason
why it increased in length but decreased in mass may have been because
the chip got “thinner” (had a smaller circumference).
0.8 molar: The potato chip in the 0.8 M sugar solution didn’t decrease as much in
length as my line of best allowed, this may have been because it didn’t
contain as much water as the others.
Conclusion:
Distilled water: My prediction for the potato chips in distilled water was correct.
Osmosis did occur and water travelled into the potato causing it to
increase in length and in mass. The potato’s cells became turgid
causing the potato to feel hard.
0.2 molar sugar solution: The potato chips in this solution did not alter much in length
or mass. I expected them to be bigger and have a higher
mass. This might have happened because the solution had
the same concentration of water as the potato.
0.4 molar: The potato chips in the 0.4M sugar solution increased slightly in
length but decreased slightly in mass. As I said in my prediction, this was a
very difficult solution to predict so, the potato chips in this solution did
follow my prediction, as it stayed practically the same.
0.6 molar: The potato chips in this solution followed my prediction, they decreased in
both length and mass. This happened because the solution outside the
potato was more concentrated than inside the potato so water travelled out
of the potato through osmosis causing the potato to become smaller and
have less mass and to become soft.
0.8 molar: The potato chips in the 0.8 molar sugar solution followed the basis of my
prediction but not as much osmosis occurred as I had expected, this could
have been because the potato chips could have dried out before I put them
into the solution.
- molar: The potato chips in this solution followed my prediction. They became
smaller and had less mass due to osmosis. They also became softer.
This shows that osmosis did occur in the potato tuber cells. The higher the concentration of sugar solution, the more water was transported out of the potato causing it to shrink in length and mass. The higher the concentration of water, the more water was transported into the potato causing it to grow in length and mass and its cells to become turgid.
Analysis:
The results show that osmosis did occur in the potato tuber cells and that the higher the concentration of sugar solution, the more osmosis occurred causing more water to travel out of the potato causing the potato to shrink in length and mass. The higher the concentration of the solution, the more osmosis occurred. This is shown on the graph as a direct relation drawn with a straight line. Osmosis occurred more in the potato in the 1M sugar solution than in the next most concentrated, 0.8M sugar solution because the 1M sugar solution was the most concentrated, which means that it had the more water molecules moved out of the potato, into the solution. This is the potato that shrank most in length and mass after 24 hours of being left in the solution as it contained less water than it had at the beginning of the experiment. The potato that increased most in length and mass was the one left in the distilled water. This was because the distilled water contained more water molecules than the potato causing the water to travel into the potato. This caused the potato’s cells to become turgid and the potato to grow in length and mass as it contained more water than it had at the beginning of the experiment. If the potato had been left for a longer period of time, some cells would have burst causing the potato to decrease in size. My conclusion supports my prediction because the potato which grew the most in length and in mass was the one in the distilled water, the one which shrank most in length and in mass was the potato in the 1 molar sugar solution. The potatoes in the other solutions followed the expected trend that the higher the concentration of sugar solution, the smaller the potato got. The only result that did not follow my prediction was the potato in the 0.6 molar sugar solution. This got smaller than I expected it to; this may have been because the potato was not left out for as long as the others and so did not loose so much water before being put into the solution.
Evaluation:
The method I used allowed me to investigate osmosis in potato tuber cells because I could easily see if osmosis had occurred in the potatoes in the different solutions and also how much water had travelled though the partially permeable membrane and whether it had travelled into or out of the potato due to osmosis. My results followed the expected trend except for the potato in the 0.6 molar sugar solution, which shrank more in length than I expected. This could have been because I may have left the other potato chips to dry out for longer and so the potato chip in the 0.6M sugar solution contained more water so more travelled out causing it to loose more mass and length than I expected. If I were to do this experiment again, I would use different test tubes for the repeats because as the potato chips in the same test tubes are affecting the amount of surface area available to water particles for osmosis as wherever you put the repeat, it is always blocking one side of the potato chip causing the results to be unreliable. Another way to improve this experiment is to make sure that the potato chips are cut, measured and weighed at about the same time otherwise; they may dry out and change in mass before they are even put into the solutions. My results are mostly reliable as they present the expected trend and support the drawn conclusion except for the anomalous result (0.6M) because osmosis occurred as expected. Further experiments will provide additional results about in osmosis in potato tuber cells by investigating osmosis to a greater degree. I should carry out more experiments on the middle two solutions i.e. 0.4M and 0.6M to make sure that I can obtain correct information as to what exactly happens to potato chips placed into these solutions.
