Investigate the Effect of Varying Solution Concentration on Osmosis in a Potato Chip

Investigate the Effect of Varying Solution Concentration on Osmosis in a Potato Chip

Prediction

A definition of osmosis is: 'the movement of water molecules from an area of high water concentration to a low water concentration across a semi-permeable membrane' (Oxforddictionary 2000).

In a high concentration of water the amount of solute (e.g. sugar) is low. These solutions are usually known as a dilute or weak solution.

But in a low concentration of water the amount of solute (e.g. sugar) is high. These solutions are usually known as concentrated or strong solutions. When a weak solution and a strong solution are separated by a partially permeable membrane, the water will move from the area of high concentration to the area of low until both sides are equal. This is osmosis, and is shown in the diagram below.

Examples of osmosis can also be seen in living cells. Root hairs on plants take in water from the soil via osmosis. Water continuously moves along the cells of the root and up the xylem to the leaf. Water is moving to areas of lower water concentration all the time. This is shown in the diagram below.

Example of Osmosis in a Root Hair Cell

When a cell is placed in distilled water which is high water concentration water will move across the semi- permeable membrane into the cell which has lower water concentration by osmosis, making the cell swell in size. The cell is now known as turgid. If a potato cell was placed in the same circumstances the cells would increase in length, volume and mass because of the osmotic effects. If the same potato cells were placed in a solution with a low water concentration, then the effects would be the opposite - water would move out of the cell into the area of lower concentration, the water. Thus, the potato chip will decrease in length, volume and mass. In more extreme cases, the cell membrane would break away from the cell wall and the cell is then known as plasmolysed.

The higher the concentration of water in the external solution, the higher the amount of water that enters the cell by osmosis. The smaller the concentration of water in the external solution, the higher the amount of water that leaves the cell. However, there will be a point where the concentrations of water inside and outside the cells are equal. This is known as the isotonic point, and at this point there will be no change in the length, vo...

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...nger, this would have enabled me to find the saturation point (when the potato can no longer take in any more water) and dehydration point (when the potato cannot lose any more water)and therefore get a more accurate result.

Finally, I could extend the experiment to a more exact level by looking at the potato cylinders under a microscope, and then I would be able to see the cells in greater detail and draw some more observational results.

Further investigations that I could carry out in the future are, using a different variety of potato, for example, a 'king Edward' rather than a 'maris piper'. Also I could use a different plant tissue, for example, a carrot or an apple. Then I could find out whether osmosis occurs with the same patterns and trends with any vegetable.

Conclusion

However despite this, I think that the experiment I carried out,

(given the apparatus I was given to carry out the test) was successful, my results were consistent, and I was pleased with the comparison of my results with my previous prediction. I followed the method plan correctly; I believe I gained accurate and sufficient enough results to conclude the experiment, and to prove my initial

prediction.