Experiment to show osmosis in potato chips in different concentrations of sucrose solution - also investigating how potato chips change in volume and weight when placed in different concentrations of sucrose solution.
Experiment to show osmosis in potato chips in different concentrations of sucrose solution - also investigating how potato chips change in volume and weight when placed in different concentrations of sucrose solution.
Introduction:
I am going to design and modify an experiment used to show osmosis in potato chips in different concentrations of sucrose solution. I am also going to investigate on how potato chips change in volume and weight when placed in different concentrations of sucrose solution. I will also conduct a preliminary experiment before my final experiment.
Aim:
To investigate the effect of different concentration of sucrose solution on potato chips.
Hypothesis:
I would expect the potato chips to turn flaccid when they are placed in a strong sucrose solution because the water from within the cells will diffuse out leaving the potato flaccid. The potato chips left in the weak sucrose solutions should turn turgid in a weak sucrose solution, due to the water being absorbed by osmosis into the cells of the potatoes, this will make the potato chip larger in size. I should also be able to find some potato chips, which have neither increased nor decreased in size because the concentration in the potato is the same as the sucrose solution, so no mass or length would be gained or lost.
Scientific knowledge:
Osmosis is a type of diffusion, where the molecules move from an area of high concentration to an area of low concentration passing through a partially permeable membrane. When distilled water or a weak sucrose solution or a diluted sucrose solution is used, the water molecules will pass through the semi-permeable membrane into the potato. This is due to the fact that the water is more concentrated outside, so the molecules in the water will move through the permeable membrane, and in this experiment it will pass through into the potato. The potato chip will increase in length, and weight due to osmosis. When a strong sucrose solution or a concentrated sucrose solution is used, the water within the potato will move out of the potato through the semi-permeable membrane, and into the strong sugar solution, of which the potato is soaked in. This will cause the potato chip to shrink in length and mass.
Further information on potato plant cells:
Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what makes the green parts of the plant "stand up" into the sunlight.
When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become "flaccid." This is the exact opposite of "turgid". The contents of the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed.
When plant cells are placed in a solution which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. "Incipient" means "about to be".
Fair Test
To make sure this is a fair test I will have to keep all the variables constant apart from the concentration. If I did change one of these variables, for example, if one potato chip were 1cm longer than the other there would be more space for osmoses to occur, therefore the test would not be fair.
To make sure the test remains fair I will do all my experiments at room temperature, use the same type of potato, which will be kept at the same size and weight and have been treated in the same way. I will also use the same volume of the solution in the test tube is kept fair. I will use an accurate electronic balance, showing grams to 2dp in this experiment, to ensure even small changes in mass are recorded. I will also keep using this balance throughout the experiment so measurements do not vary due to any change that may be introduced by different scales.
Key Variable:
Independent variable/s: concentration
Dependant variable/s: mass, length, volume of solution
Controlled variable/s: temperature, size of chip, time
Concentration is an independent variable because we can control and change the concentration to our desired concentration.
Mass, length and volume are dependant variables because our whole experiment depends on these variables, which we can alter and change to a desired amount.
The temperature and time are controlled variables because they should be kept the same for each potato chip and solution through-out the experiment because temperature is a catalyst and may speed ...
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Key Variable:
Independent variable/s: concentration
Dependant variable/s: mass, length, volume of solution
Controlled variable/s: temperature, size of chip, time
Concentration is an independent variable because we can control and change the concentration to our desired concentration.
Mass, length and volume are dependant variables because our whole experiment depends on these variables, which we can alter and change to a desired amount.
The temperature and time are controlled variables because they should be kept the same for each potato chip and solution through-out the experiment because temperature is a catalyst and may speed up osmosis if the best temperature is reached, and if the temperature is too hot it may damage the cells in the potato chips.
Risk assessment:
Risk
Precaution
Spilling sucrose solution
Wear a lab coat and goggles to protect your clothes and eyes from the sucrose solution. If the sucrose solution gets into the eyes use some eye wash to wash your eye and then find a teacher and explain the situation.
Preparing the potato for the chipper
The side of the potato are not flat so you will have to take precaution when cutting the sides off for the potato chipper.
Preliminary Experiment
Aim:
To have a practice run of the actual experiment and make alterations and improvements to the method designed, so that when the final experiment is held, there would be less criticisms and more reliable results.
Apparatus list:
Beakers (3)
Digital balance
Forceps
Petri-dish
Measuring cylinder
Stop clock
Scalpel
Ruler
White tile
Potato (1-2)
Paper towels
Sticky labels
Method:
Prepare the potatoes by cutting the edges of the potatoes and cutting the potato into chips with the scalpel, on a white tile.
Pick up the chips using forceps because if the potato chip was help with fingers then dirt on the hands may alter the reliability of the results.
Pick out six of the chips, which are most suitable, and throw away any odd shaped potato chips. If there is any skin left on the potato chip you can remove the skin by cutting it off with a scalpel
Measure the sides of the potato chips so all the chips have relatively the same volume. If one chip is slightly longer than the others, by using a scalpel you can cut away the extra part
Place the potato chips into three groups so they're in pairs. Then label the groups, A, B, and C.
Label your six chips by inserting different coloured pins into the potato chips and note down on the results table which coloured pin is inserted into which chip. Another coloured pin should also be inserted to represent its group. So as a result you should have potato chips labelled A1, A2, B1, B2, C1 and C2
Measure the weight of each individual chip by placing a petri dish onto a digital balance and then tearing the weight away. Then place the potato chip onto the petri dish and record the mass on the table.
Collect three beakers and label the beakers A, B, and C, by using a china graph pencil or by attaching a sticky label onto the beaker.
In beaker A, using a measuring cylinder measure out 120ml of water and pour the water into beaker A.
In beaker B, using a measuring cylinder measure out 60ml of water and 60ml of sucrose solution, mix the two together and pour into beaker B.
In beaker C, using a measuring cylinder measure out 120ml of sucrose solution and pour it into beaker C
Place potato chips A1 and A2 into beaker A. Leave a two-minute gap and then repeat with potato chips B1 and B2 and beaker B. leave another two-minute interval and repeat again with potato chips C1 and C2 and beaker C.
Cover the beakers with cling film preventing the solution form evaporating
Leave the potato chips in the solution for a minimum of half a day.
After leaving the potato chips in for half a day remove potato chips from beaker A and blot the potato chip dry to remove any excess water or solution and measure the masses and the length. Try to complete this part in two minutes and then repeat the process with the other two solutions.
Results: Mass
Concentration of sucrose solution and Beaker reference letter
Potato chip
Mass before (1/10 of a gram)
Mass after (1/10 of a gram)
Change in mass (1/10 of a gram)
Percentage change in mass
O.O (A)
A1
0.4
1.9
+1.5
+14.4%
A2
9.7
0.9
+1.2
+12.4%
Average:
N/A
0.1
1.4
+1.3
+13.4%
0.5 (B)
B1
0.2
8.4
-1.8
-17.6%
B2
0.3
8.7
-1.6
-15.5%
Average:
N/A
0.3
8.6
-1.7
-16.55%
.0 (C)
C1
9.9
6.4
-3.5
-35.4%
C2
0.0
6.3
-3.7
-37.0%
Average:
N/A
0.0
6.4
-3.6
-36.2%
Results: Length
Concentration of sucrose solution and Beaker reference letter
Potato chip
Length before (cm)
Length after (cm)
Change in length (cm)
Percentage change in length
O.O (A)
A1
6.2
6.2
0.0
0%
A2
6.2
6.2
0.0
0%
Average:
N/A
6.2
6.2
0.0
0%
0.5 (B)
B1
6.2
5.5
-0.7
-11.3%
B2
6.2
5.3
-0.9
-14.5%
Average:
N/A
6.2
5.4
-0.8
-12.9%
.0 (C)
C1
6.2
5.3
-0.9
-14.5%
C2
6.2
5.2
-1.0
-16.1%
Average:
N/A
6.2
5.3
-1.0
-15.3%
Analysis:
By looking at the graphs produced by plotting the concentration on the x-axis and the percentage change on the y-axis there are no obvious anomalies. The mass of the potato chips are decreasing in length and mass as the concentration increases, as shown by the graph and the results table, this proves my hypothesis on osmosis was correct.
The graph to show the percentage change in mass has a relatively good line of best fit. Where as the line of best fit on the graph to show the percentage change in length over the concentration has a very poor correlation and so a poor line of best fit.
Graphs:
See graph paper.
Evaluation:
Studying the results I obtained I realized that having three different concentrations were not enough, and I could increase the amount to six different concentrations.
I only placed two potato chips into each solution, there weren't enough results and so to increase the reliability I will also increase the amount to three potato chips to each beaker.
The length was hard to measure accurately, and so if I were a millimetre out it would have made a large percentage difference. I also realized that that length was very hard to measure and was difficult to measure the length precisely and weight the mass of the chips in two minutes.
I have decided to measure the volume of solution instead of the length for my actual experiment, because the volume of solution is a lot easier and quicker to measure and is also more accurate. I will also be changing the volume of solution to 100cm3 of water, because 120ml was hard to calculate the percentage and so using 100ml3 would be easier to work out the percentage.
The results collected are rather poor. There aren't enough concentrations for me to plot a good graph. It is also very hard to plot the graph when one of the results is an anomaly, and because there are only three concentrations it is very hard to defy which one is the anomaly, and even whether there are any anomalous results plotted.
Conclusion:
I have made some changes to my method and will be using the new method for my actual experiment.
Final Experiment
Introduction:
I have done my preliminary experiment and with the experience gained from the experiment I have re-written the method and apparatus list to fit my new method. My experiment should work better this time due to the numerous changes and improvements made.
Aim:
To investigate the effect of different concentration of sucrose solution on potato chips.
Hypothesis and Background knowledge:
These remain the same as the ones set before.
Apparatus list:
Beakers (6)
Digital balance
Forceps
Petri dish
Measuring cylinder
Stop clock
Scalpel
White tile
Potato (1-2)
Paper towels
Sticky labels
Ruler
Method:
Prepare the potatoes by cutting the edges of the potatoes and cutting the potato into chips with the scalpel, on a white tile.
Pick up the chips using forceps because if the potato chip was help with fingers then dirt on the hands may alter the reliability of the results.
Pick out eight-teen of the chips, which are most suitable, and throw away any odd shaped potato chips. If there is any skin left on the potato chip you can remove the skin by cutting it off with a scalpel
Measure the sides of the potato chips so all the chips have relatively the same volume. If one chip is slightly longer than the others, by using a scalpel you can cut away the extra part
Place the potato chips into six groups so there are three potato chips in each group. Then label the groups, A, B, C, D, E, F
Label your eight-teen chips by inserting different coloured pins into the potato chips and note down on the results table which coloured pin is inserted into which chip. Another coloured pin should also be inserted to represent its group. So as a result you should have potato chips labelled A1, A2, A3, B1, B2, B3, C1...etc
Measure the weight of each individual chip by placing a petri dish onto a digital balance and then tearing the weight away. Then place the potato chip onto the petri dish and record the mass on the table.
Collect six beakers and label the beakers A, B, C, D, E, F, by using a china graph pencil or by attaching a sticky label onto the beaker.
In beaker A, using a measuring cylinder measure out 100ml of water and pour the water into beaker A.
In beaker B, using a measuring cylinder measure out 80ml of water and 20ml of sucrose solution, mix the two together and pour into beaker B.
In beaker C, using a measuring cylinder measure out 60ml of water and 40ml of sucrose solution, mix the two together and pour into beaker C.
In beaker D, using a measuring cylinder measure out 40ml of water and 60ml of sucrose solution, mix the two together and pour into beaker D.
In beaker E, using a measuring cylinder measure out 20ml of water and 80ml of sucrose solution, mix the two together and pour into beaker E.
In beaker F, using a measuring cylinder measure out 100ml of sucrose solution and pour into beaker F.
Place potato chips A1, A2 and A3 into beaker A. Leave a two-minute gap and then repeat with potato chips B1, B2, and B3 into beaker B. leave another two-minute interval and repeat again with potato chips C1, C2and C3 into beaker C...etc.
Cover the beakers with cling film preventing the solution form evaporating
Leave the potato chips in the solution for a minimum of half a day.
After leaving the potato chips in for half a day remove potato chips from beaker A and blot the potato chip dry to remove any excess water or solution and measure the masses. Repeat for all the other chips
Using a measuring cylinder pour the solutions into the measuring cylinder and measure the volume of solution and take down the results, repeat this for every other solution.
Results: Mass
Concentration of sucrose solution and Beaker reference letter
Potato chip
Mass before (1/10 of a gram)
Mass after (1/10 of a gram)
Change in mass (1/10 of a gram)
Percentage change in mass
0.0 (A)
A1
8.09
8.89
0.80
9.89
A2
8.99
0.02
.03
1.46
A3
8.60
9.60
.0
1.63
Average:
8.56
9.50
0.94
0.99
0.2 (B)
B1
8.62
8.94
0.32
3.71
B2
6.41
6.82
0.41
6.40
B3
8.06
8.48
0.42
5.21
Average:
7.70
8.08
0.38
5.11
0.4 (C)
C1
4.72
4.75
0.03
0.64
C2
7.21
7.13
-0.08
-1.11
C3
8.31
8.15
-0.16
-1.93
Average
6.75
6.68
-0.07
-0.8
0.6 (D)
D1
6.64
5.72
-0.92
-13.86
D2
6.84
5.85
-1.61
-23.54
D3
6.39
5.44
-0.95
-14.87
Average
6.62
5.67
-1.16
-17.42
0.8 (E)
E1
5.61
4.41
-1.2
-21.39
E2
4.28
3.20
-1.08
-25.23
E3
8.40
6.77
-1.63
-19.40
Average
6.10
4.79
-1.30
-21.31
.0 (F)
F1
7.37
5.78
-2.62
-35.55
F2
7.09
5.55
-1.54
-21.72
F3
8.29
6.39
-1.9
-22.92
Average:
7.58
5.91
-2.02
-26.73
Anomalous results are highlighted in the table
Results: Volume of solution
Concentration of sucrose solution and Beaker reference letter
Potato chip
Volume before (cm3)
Volume after (cm3)
Change in volume (cm3)
Percentage change in volume
0.0 (A)
A1
00
95
-5
-5
A2
A3
Average:
00
95
-5
-5
0.2 (B)
B1
00
97
-3
-3
B2
B3
Average:
00
97
-3
-3
0.4 (C)
C1
00
98
-2
-2
C2
C3
Average
00
98
-2
-2
0.6 (D)
D1
00
02
2
2
D2
D3
Average
00
02
2
2
0.8 (E)
E1
00
04
4
4
E2
E3
Average
00
04
4
4
.0 (F)
F1
00
05
5
5
F2
F3
Average:
00
05
5
5
Anomalous results are highlighted in the table
Analysis:
I used the results collected from the experiment and plotted two different graphs, one to show the percentage change in mass over the concentration, and the other graph was the percentage change in volume over the concentration. The lines of best fit are good and so is the correlation of the points plotted. There are no obvious anomalies to investigate the effect of different concentration of sucrose solution on potato chips, and a clear line of best fit proves my hypothesis.
The lines of best fits are straight lines and aren't bent, this means the concentration and the percentage change is proportional.
Once again my graphs prove that my prediction on how potato chips decrease in size as the concentration increases was proven.
I have realized that the volume of solution also increases as the concentration increases, and so when there is a low concentration the volume also decreases.
Graphs:
See graph papers
Scientific explanation:
The volume of water increase as the concentration becomes stronger, this is because the water in the potato chips' cells are in the area of high concentration and so the water moves out of the cells and into the solution. So when a weak solution is used the sucrose solution is more concentrated than the water within the potato cells, therefore the solution moves into the cells and so the volume of solution will decrease and the size of the potato chip increase.
Evaluation:
My results were better this time, but I still remain unsatisfied with the amount of results gathered. I think the experiment would of worked better if I could use more potato chips. Instead of only using three potato chips to a concentration I think I could of used five potato chips instead.
When I did this experiment I was limited to half an hour to set up everything and so it was very rushed and I didn't have enough time to make my measurements accurate.
Cutting the potato chips to all the same dimensions was very difficult because the dimensions are very small.
The apparatus used was also very inaccurate, for instance instead of using a measuring cylinder I could have used a burette to make the reading more accurate.
I increased the amount of concentrations from three to six but I still think six solutions are still very unreliable and that it should be ten or twenty different concentrations.
When the experiment was conducted the temperature was not kept the same and this could increased or decreased the rate of which osmosis took place.
Conclusion:
Overall I think my experiment was relatively good, and if more modifications were made the experiment could have been better. My results were fair and I am pleased with the results.
Secondary sources
- GCSE Biology revision guide by 'The Science Co-ordination group' (page 5)
- Microsoft Encarta
Biology Coursework, Matthew Cox