There is a limit to how much osmosis will occur. This is because the potato contains a limited amount of water. If too much water leaves the cells inside the potato they destroy themselves because the cell membrane becomes detached. This is called plasmolysis.
Prediction:
Using the theory of osmosis it can be predicted that if a potato chip has a ratio of 99 parts water to 1 part potato, the mass will decrease when it enters a solution of salt water higher than 1% salt and increase when it enters a solution of salt water lower than 1%. When the potato chip is put in a flask containing exactly 1% salt no change will take place, as the amount of water is equal in both the solution and the potato. This is shown by the diagram overleaf:
I predict that in the 5% salt solution the potato chip will decrease in mass significantly. When the potato enters the 4% salt solution it will still decrease only not by as much. At 1% salt solution the amount of water inside and outside the potato chip is equal and therefor it is not possible for osmosis to take place. In the pure water the potato chip has a lower concentration of water molecules than inside the flask, hence osmosis will have the opposite affect and the mass of the potato will increase.
Fair Test and Safety
To make sure this experiment is a fair trial I will:
1 Make sure the potato chips are identical in mass and size
2.Make sure the physical elements of every piece of potato remain constant before entering the beaker
3.Make sure the temperature of the beaker remains constant
As this experiment doesn’t use heat or dangerous chemicals the safety procedures can be overlooked, but just in case my team will wear goggles and take care at all times.
Apparatus:
- Potato
- Potato corer
- Pure distilled water
- Salt Solution
- Beaker
- Digital top pan balance
- Paper towels
Diagram
Method
- I will cut six identical pieces of potato with a potato corer
- I will weigh these chips to make sure they have the same mass
- I will fill a beaker up with 5% salt solution, so 95% water
- I will place the potato chip inside the beaker
- After a day I will take the potato out and weigh it again
- This result will tell me how much Osmosis has taken place
- I will record this result in a table
- I will clean out the beaker thoroughly making sure the temperature stays the same
- I will repeat the last five steps for
- 4% salt solution (96% water)
- 3% salt solution (97% water)
- 2% salt solution (98% water)
- 1% salt solution (99% water)
- 0% salt solution (100% water)
To make my results even more accurate I will take these recording three times
Analysis
We decided to take the measurements three different times and work out the mean to plot the graph because we thought that this was the best way of getting definite accurate results without using up all our time.
Conclusion
Although the results do not match exactly to the theory of Osmosis the general trend can be seen especially if the average change is looked at. Although the percentage change on each different trial doesn’t agree completely with my prediction it is only by a few percent. I believe that with the use of more efficient equipment and if more care was taken my prediction would be proved correct.
Evaluation
My results give the impression that as the amount of salt in the salt solution increased the change of mass decreased. This is what I predicted.
I did encounter one mistake in my obtaining in the first trial of the 4% salt solution. This may be due to a very slight increase in the amount of the salt solute or in the mass of the potato chip, that was not picked up on the scales. Or a rise in temperature around this flask. To keep my graph accurate I left this out of the average.
If I were to repeat the experiment I would take more care in measuring the equipment.
