Introduction
The aim of this specific lab is to determine the biological changes that occur to potato slices over a period of time in different solutions and to relate these changes to the phenomenon of osmosis.
By placing pieces of a potato into solutions with different concentrations of solute, water may flow into or out of the potato. Knowing whether or not water flowed into or out of the potato will give you an idea of approximately what percentage of a potato is water.
The concentration of solutes in water is low or nonexistent. Therefore, water is hypotonic to the fluid. If the potatoes are placed in a solution with a high concentration of solute compared to the potatoes, water will pass through the cell membranes into the surrounding hypertonic solution, and the potatoes will shrink, or plasmolyze.
The selectively permeable membrane of potato allows water to pass through in response to concentrations of the solutions on either side of the membrane. The water will move toward the more hypertonic, or highly concentrated, solutions.
Research Question
What is the effect of varying sucrose solution on mass of potatoes due to phenomenon of osmosis?
Hypothesis
If the concentration of sucrose solution increases the mass of sliced potato will decrease due to osmosis.
Explanation of the Hypothesis
* diffusion - the movement of molecules from an area of high concentration to an area of low concentration
* osmosis - the diffusion of water
* plasmolysis - a type of osmosis in which water moves out of the material
* deplasmolysis - a type of osmosis in which water moves into the material
* isotonic solution - a solution with equal concentration of solute inside and outside of the material
* hypertonic solution - a solution with more solute in the surrounding environment than in the material
* hypotonic solution - a solution with less solute in the surrounding environment than in the material
Osmosis is the diffusion of water down its concentration gradient. In all cells, survival depends on the ability to maintain homeostasis by regulating the movement of molecules across the cell membrane. In osmosis, water molecules move across a selectively permeable membrane toward a solution with a higher concentration of solutes. The molecules continue to move until equilibrium is reached that ...
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* hypertonic solution - a solution with more solute in the surrounding environment than in the material
* hypotonic solution - a solution with less solute in the surrounding environment than in the material
Osmosis is the diffusion of water down its concentration gradient. In all cells, survival depends on the ability to maintain homeostasis by regulating the movement of molecules across the cell membrane. In osmosis, water molecules move across a selectively permeable membrane toward a solution with a higher concentration of solutes. The molecules continue to move until equilibrium is reached that is, equal concentrations of water molecules and of solute molecules on either side of the membrane.
Variable
Dependent
the percentage gain or loss of the mass of the potato slice
Control
Independent
Percentage of sucrose concentration in the solution
- range of 0%,2.5%,5%,10% and 50%
Fixed
Surface area of peeled Potato =Approx 12.5 cm2
Initial Mass of potato = 26.0 g
Distilled Water =100ml
4 of equal 200ml beakers
Time Range of experiment - 23 hours & 12 min, 26 hours & 7min
Uncontrolled
Temperature of experiment location
Type of Potato
Materials
Four 200ml beakers
Fine Potato (es)
Potato Peeler & Knife
Electronic balance
Graduated cylinder
Masking Tape
Food Film/Rap
Sucrose
Source of distilled water
String rod
Spoon
Paper towel
Procedure
. In order to determine if the salt in the water has an effect on the potato cells, one need to cut four equal sized slices of peeled potato. The best way to do this is to Using the knife, carefully cut each potato core into a flat cylinder of about two to three centimeters thick, so that one can compare the effects of the water and the sucrose. In order to draw any conclusions, the potato slices must be exactly the same size to begin with. It is important to enter the mass of the potato slices into the data table so you can compare it to the size of the potato slice the next day.
2. Slice each potato to a mass of 26 grams. NOTE : each potato doesn't have to be 26 grams. The goal is to end up with four potato slices of exactly the same mass.
3. Using the balance, measure and record the mass of each potato slice.
4. Fill the graduated cylinder with distilled water preciously 100ml of water up. Then pour 100ml of water into a beaker.
5. Calculate the mass of sucrose needed to reach the certain concentration for each different beaker. Achieve 0%, 2.5%, 5%, 10% and 50% of sucrose concentration and label each beaker with certain percentage rate.
6. Attach each potato core, one at a time, to the end of the spoon and hold it so that the potato core is completely submerged in the water. Record the time when all potatoes were submerged.
7. Cover the top of each beaker with a piece of food film. Fold the food film down and seal along the sides of the beaker with masking tape.
8. Allow the beakers to sit for preciously 24 hours.
9. Remove the cores from each beaker using the spoon. Measure and record the mass of each potato slice as one did earlier.
Data
Trial 1
Concentration
Initial
Final
Change
Result
0.0%
26.00
30.60
4.60
Hypotonic Solution
2.5%
26.00
29.80
3.80
5.0%
26.00
28.90
2.90
0.0%
26.30
26.20
-0.10
Isotonic- above 10%
50.0%
26.20
9.00
-7.20
Hypertonic Solution
Trial 2
Concentration
Initial
Final
Change
Result
0.0%
25.90
30.10
4.20
Hypotonic Solution
2.5%
26.10
29.60
3.50
5.0%
25.90
29.20
3.30
0.0%
26.00
26.00
0.00
Isotonic Solution
50.0%
26.00
9.20
-6.80
Hypertonic Solution
Trial 3
Concentration
Initial
Final
Change
Result
0.0%
26.10
30.50
4.40
Hypotonic Solution
2.5%
25.90
29.30
3.40
5.0%
25.90
29.00
3.10
0.0%
26.20
26.10
-0.20
Isotonic- above 10%
50.0%
26.00
9.10
-6.90
Hypertonic Solution
Graphs Trial 1
Trial 2
Trial 3
Conclusion
According to the hypothesis if the concentration of sucrose solution increases the mass of sliced potato will decrease due to osmosis by becoming a hypertonic solution. After the experiment there was a significant result of achieving a hypertonic solution with highest concentration thus proving that higher concentration leads to decline of mass of sliced potato due to osmosis.
When potatoes are placed in a solution with a high concentration of sucrose compared to the potatoes, water will pass through the cell membranes into the surrounding hypertonic solution, and the potatoes will shrink, or plasmolyze.
Explanation of Conclusion
By placing pieces of a potato into solutions with different concentrations of solute, water may flow into or out of the potato. Knowing whether or not water flowed into or out of the potato will give you an idea of approximately what percentage of a potato is water.
The concentration of solutes in water is low or nonexistent. Therefore, water is hypotonic to the fluid. If the potatoes are placed in a solution with a high concentration of solute compared to the potatoes, water will pass through the cell membranes into the surrounding hypertonic solution, and the potatoes will shrink.
The selectively permeable membrane of potato allows water to pass through in response to concentrations of the solutions on either side of the membrane. The water will move toward the more hypertonic, or highly concentrated, solutions.
Evaluation of Results
The value of trial 2 and 3 were reliable due to its closeness in value. As well I achieved the accurate isotonic solution at sucrose concentration of 10 %. The standard deviations of all three trials are excessively large since I included 50% of sucrose concentration as a maximum. According to the data chart, throughout all trials, I was able to accomplish hypotonic solution at 0 % concentration, hypertonic solution at 50% concentration and reasonable isotonic solution near 10%. During the trail 2, I derived preciously 0 g of mass change becoming a solid evidence of isotonic solution; however other two isotonic solutions could be considered inaccurate due to closeness to 0g of -0.1 g of mass change. I would suspect a simple inaccuracy or recording error measuring the mass of sucrose or the initial mass of potato.
Evaluation of the Procedure
The goal, previously mentioned, was to end up with four potato slices of exactly the same size. However, during this experiment, the mass of the each potato slices were accurate however, I was less careful on volume and surface area. Thus one of improvement can be done by squaring off the ends of the potato to at least 8 cm long. Stand it on end and bore three vertical holes. Space them close together so that one or two other groups can use the rest of the potato. As well, recording the difference of volume and surface area including mass will increase the reliability and accuracy of Osmosis lab.
