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Osmosis in a Patato Chip

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Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size.


Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato chip of a given size.

Osmosis is defined as the net movement of water or any other solutions molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with all areas having an equal concentration.

For this particular investigation I think that the lower the concentration of the sugar solution in the test tube, the larger the increase in mass of the potato chip will be. This is because the water molecules pass from a high concentration. Therefore, I believe that the chips that are in the tubes containing a higher concentration of water than sugar will have a larger mass than chips in tubes with higher sugar concentrations.

Further information on potato plant cells:

Plant cells always have a strong cell wall surrounding them. When they take up water via osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. The definition of Turgid is when a cell becomes 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 due to the process of osmosis, and they become "flaccid." This is the exact opposite of "turgid". The content of the potato cells shrinks, and consequently 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".

In order to create a fair test certain aspects of the experiment will have to be kept the same whilst some key variables are changed. In this test I will be changing the concentration of the sugar solution and water whilst keeping the time limit and the mass of the potato chip the same. This will give me a very varied set of results from which I hope to make a decent conclusion. If any of the non-variables below were not kept constant it would mean it would not be a fair test. For instance if one of the potato chips was 1mg larger in mass than the others, the surface area of the chip would be larger and there would therefore be more space for osmosis (transportation of materials between two regions) to occur.

At the beginning of the experiment all the potato chips will be 2mg in mass. There will be 6 test tubes each containing 3 2mg potato chips. Each tube will contain 10ml of solution, some with more water than others. The table below shows the details at the start of the experiment.

Mass at mass at change in Average

Start (g) End (g) Mass (g) change

Concentration 1 2 3 1 2 3 1 2 3 1 2 3

1M 2.0 2.0 2.0 1.9 1.9 1.9 -1 -1 -1

0.8M 2.0 2.0 2.0 1.7 2.0 1.9 -1 0 -1

0.6M 2.0 2.0 2.0 1.7 2.1 1.9 -1 -1 -1

0.4M 2.0 2.0 2.0 2.0 1.9 2.0 0 -1 0

0.2M 2.0 2.0 2.0 1.9 1.9 2.0 -1 -1 0

H20 2.0 2.0 2.0 1.9 2.0 1.9 -1 0 -1

These preliminary test results give me an overall impression on the change in mass gain or loss when placed in varying concentrations of sucrose solution.

Planned method:

There will be 6 test tubes each containing a different amount of cold water and a sugar solution i.e. sucrose. Sections of potato will be cut using a scalpel and will be measured using a ruler. This part of the preparation must be done very accurately as a change in the surface area may allow more or less osmosis to occur. The mass of each chip will be measured as well so that more results can be obtained. Three chips will be placed in each test tube each time so that I can take an average for each tube. Then the potato pieces will be removed, the surface solution removed using paper and then they will be reweighed. If I then have time afterwards I will repeat this experiment again as to obtain a second set of results. This will hopefully produce more accurate results from which I will be able to draw a more accurate conclusion.

Obtaining evidence


1. Using a scalpel and weight machine I cut the potato chips into 18 small pieces, which were all 2.0mg in weight.

2. Taking a test tube rack I placed 6 test tubes and then labelled them H2o to 1.0M.

3. Using a measuring cylinder I measured out different amounts of sucrose solution and water, which I then poured into the test tubes giving10M equal volumes.

4. I then weighed every potato chip on an electronic balance and recorded the weights.

5. I swiftly put 3 potato chips into each beaker and then started my stopwatch. 3 chips were used to create an average, which gave me a better set of results and more accurate graphs.

6. After 1 hour 15 minutes I drained out the solutions in the sink and placed all the chips on the paper in the order I had put



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