Fair test
To ensure it is a fair test I will:
- Try to make all my potato chips the same size (30mm) and weight (around 4.4g) so the my experiment is not biased
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I will put an equal amount of liquid (volume = 10.5ml3) in each boiling tube and ensure each of the chips are fully submerged in the liquid.
- I will make sure I leave each chip in for the same length of time (20mins)
- I will record the mass and weight of the potato chip before and after they have been in the liquid so that I can see the changes.
- I will record the volume of liquid in the boiling tube before I put the potato chip in.
- The potato chips must all be as close to the same weight as possible.
- The potato chips must all have the skin removed because the skin can stop Osmosis working to its potential.
- I will use tweezers to put the potato chips in the boiling tubes and also to remove them.
- All the potato chips will go into the boiling tubes at the same time.
- I will dry all the potato chips in green paper towels for the same amount of time and the same way.
Prediction
My prediction is that the potato chip in the boiling tube with the most concentrated sucrose solution will drop in mass and length after the 20 minutes is up because of Osmosis, and the potato chip in the most dilute solution will become longer and the mass will increase.
I would expect a graph of my results to look something like this:
Explanation of Prediction:
I predicted that the potato chip in the boiling tube with the most concentrated sucrose solution will drop in mass and length after the 20 minutes is up. My reason for this prediction is by looking at the definition of osmosis: osmosis is the movement of water particles from a weaker solution to a stronger solution through a partially permeable membrane. By understanding this you will see that when the potato chip is in the more concentrated solution it itself is the weaker solution and the cell walls of each cell in the potato are the partially permeable membrane. So, the water particles in the potato chip (the weaker solution) move through the cell wall (partially permeable membrane) and into the concentrated sucrose solution (the stronger solution). Therefore the potato chip looses its mass and the length decreases.
On the other hand the potato chip in the most dilute solution will become longer and the mass will increase. This is because the weak sucrose solution (the weaker solution) passes into the cells of the potato chip through the partially permeable membrane of the cell wall and into the potato chip making all the cells become turgid an increase the volume of the chip.
Preliminary work:
During the preliminary experiment some problems arose that I didn’t think of before. Such as: leaving bits of skin on the potato chips, cutting the chips into unsuitable shapes so making it harder to get the chips to a similar mass and length, getting the chips mixed up and drying them in different ways. All of these things mean that I didn’t make it a fair test so my results were not accurate enough.
For the real experiment I took much more care and followed the instructions more accurately.
The preliminary experiment helped me decide how many potato chips to test on to achieve the right amount of results to analyse. Also what concentration to put the sucrose solution at to be able to see exactly how it affects the chip and.
Obtaining evidence – the results
Safety
I made this experiment safe by taking precautions to minimise the hazards. When using the knife to cut my potato chips I ensured I paid a lot of attention and didn’t get distracted so that I wouldn’t cut my fingers. I cut the potatoes onto a white slate so as not to damage the tabletop. I was careful not to spill any of the sucrose solution on the floor, which could cause a hazard because it would make the floor slippery. I wore an apron to ensure that I didn’t spill any of the sucrose solution on my clothes, I wore goggles to ensure I didn’t get any sucrose solution in my eyes. I was also careful when handling the glass boiling tubes.
Table of results to show the osmosis in potato chips
Experiment 1
Experiment 2
Experiment 3
Analysing and considering evidence
My evidence shows that the stronger the sucrose solution, the greater the decrease in mass in the potato chip, and the weaker the sucrose solution the smaller the decrease in mass in the potato chip. However the distilled water and the 0.25 molar sucrose solution made the chip increase in mass, this is due to osmosis. The definition of osmosis is: the movement of water particles from a weaker solution to a stronger solution through a partially permeable membrane.
From my graph I can see that the line that shows the mass of the potato chip before I put it in the solution (the blue line) is relatively even, this is because I tried to ensure that my potato chips were all approximately the same mass before they went into the solution. The line that shows the mass of the potato chip after they have been in the solution(the pink line) however has changed dramatically, it stays a similar shape to the original line but exaggerates all the points. The graph shows that the chip in the distilled water and the chip in the 0.25 molar sucrose solution increased in mass, this is because (going by the rules of osmosis) the liquid in the cells of the potato is a stronger solution than the distilled water or 0.25 molar sucrose solution therefore the water particles pass through the cell wall (partially permeable membrane) of the potato and into the cell, making it become turgid and increase in mass. The chip in the sucrose solution any higher than 0.25 molar however is a stronger solution than the potato chip cells so the water particles from the potato chip cells move through the cell wall and into the solution making the potato chip cells become flaccid and decreasing the mass. You can see all of this in the graph, the first two point of the graph in pink are above the first two points in blue and the remaining three are all below.
These graphs show similar results to my graph for experiment 1, this suggests that all three of my experiments were relatively equal. However the last point on graph 3 goes down from the previous point I think I must of made a mistake in my calculations or I may of taken the potato chip out at a slightly different time to the other two or possibly I dried it differently.
These graphs didn’t turn out how I expected, but they still show the point that the solution is equal to the potato (the point at which the line crosses the axis). Graph two and three are very similar but graph 1 is a bit different, I think this may be to do with the fact that my piece of potato for the 1 molar solution is slightly larger than the others.
Results compared to predictions
My results in general do follow my predictions, my original predictions were: that the potato chip in the boiling tube with the most concentrated sucrose solution will drop in mass and length after the 20 minutes is up because of Osmosis, and the potato chip in the most dilute solution will become longer and the mass will increase. This was proved true by my experiments. However I expected my graph to look slightly different to what it did.
Evaluation
I think that the quality of my results were relatively consistent and good. I took care to write my results down accurately and ensured all of my experiments were fair and unbiased.
