Potato Chips Investigation

Potato Chips

Plan

Using cork bore, cut out fifteen potato chips. I am using a cork borer so that the chips have an equal diameter. Then measure the chips with a ruler so that the chips are all exactly five centimetres long. Place three chips into each of the five boiling tubes. In the first place 100% salt solution, in the second, 75% solution, in the third, 50%, in the fourth, 25% and in the fifth, 0% solution (100% water). All test tubes must have exactly 100ml of solution in them. I will measure the mixtures with a measuring cylinder for accuracy. Then place the five tubes in a test tube rack and make sure they are labelled. Then leave for twenty-four hours before examining them to obtain results.

After twenty-four hours we drained the liquid out of each test tube and removed the potato chips. We placed them on the white tile and measured them with a ruler.

Fair Test

The key factors of the fair test are that the potato chips start off at exactly the same length and width. They also must be kept at the same temperature, they must all have the same surface area and all spend the same amount of time in the solution.

We will change the concentration of the solution within each boiling tube to gain our results. However, we must keep the amount of concentration the same at 200ml.

Apparatus

5 boiling tubes
1 large potato
Test tube rack
Cork borer
Ruler
Measuring cylinder
White Tile
100% Salt Solution (NaCl)
100% Water (H2O)

Scientific Explanation

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We will change the concentration of the solution within each boiling tube to gain our results. However, we must keep the amount of concentration the same at 200ml.

Apparatus

5 boiling tubes
1 large potato
Test tube rack
Cork borer
Ruler
Measuring cylinder
White Tile
100% Salt Solution (NaCl)
100% Water (H2O)

Scientific Explanation

Plant cells have a cell surface membrane, but outside this is the cellulose cell wall. Inside a plant cell there is a solution of salts and other solutes, many of which are located in the vacuole. The cell surface membrane is partially permeable. But the cellulose cell wall is fully permeable to solutes as well as water.

If you immerse a plant cell in water, the water flows through the cell wall and cell surface membrane into the vacuole from the outside. As a result, the cell swells up. But it doesn’t burst because the cell wall stops it expanding too much. The wall stretches but it doesn’t break. When this point is reached, we say the cell is turgid.

Results

All of our chips started at 50mm, here are the results after 24hours in the solutions:

Our results were very pleasing; we felt that there was no need to repeat the experiment. The cells which had become longer now felt hard and had become turgid. The cells which had become smaller in length felt very floppy and had become flaccid. This is because all the moisture has been lost from the turgid chips, and more moisture has been added to the chips which have turned flaccid through osmosis.

I have rounded these results to the nearest whole number to make the results easier to understand, and the pattern should now be clearer.

Explanation

From our results I have found out that the potato chips have expanded in length when the concentration of salt is low, and they have decreased in length when the concentration of salt is high. It is shown clearly in the results table above that the higher the concentration of water, the more the potato chips have expanded. You can see from my graph that the general trend is that the higher the concentration of water, the more the chip has expanded. Also, the lower the concentration of water, the more the chip decreases in size.

Graph

I then decided to present my findings in a graph. First I took an average length of the chips from each solution. I did this by adding the three lengths together, then dividing them by three. I then rounded of the average to the nearest whole number so it would be easier to work with. My average potato chip lengths are:

Then I designed and plotted a graph to show my results more clearly. (See graph attached) On the graph I have drawn a line to show a line of best fit to show the general pattern of the chips from each test.

Conclusion

From my graph, I conclude that the potato chips have expanded in length in a low salt solution because the concentration of water is higher outside the chip than inside. The potato chips in the higher salt solutions have decreased in length because the concentration is higher inside the chip than outside. Osmosis causes the water to move through the semi-permeable membrane of the chips cell wall. I understand that osmosis is the movement of water through a semi-permeable membrane. The water moves from the high concentration of water to the low concentration of water.

Evaluation

I was extremely pleased with the results I obtained. I think they were reasonably accurate and I had no anomalous results. The suitability of the procedure was excellent and proved osmosis well. For more accuracy, I think we could have used more potato chips, so that we could achieve more accurate averages to plot the graph.

I found the reliability of the results good, and think that the evidence is sufficient to prove the process of osmosis. To further this work, I could try different vegetables in different solutions. For example a sugar solution, this would allow me to gain more results.