Preliminary Work: We did a preliminary test to see if our predicted solutions were reasonable ones. They were as the weight gain and lose were what was expected to happen.
Variables: We can change the salt solution percentage, temperature of the water, starting size of the chip, type of potato as they can be more expensive, genetically made and had extra fertilisers added to them.
I am going to change the salt solution percentage, as the chip shop would always use the same type of potato and same size. Also the water temperature would be kept at the same. So changing the salt solution will help us find out the aim of why the chip changes size.
Measurements: We will be measuring the weight gain or lose of the chips that have been put in the salt solution after half an hour. Two chips will be placed into the salt solution and the weight will be the combined weight of both chips before being put into the solution and after being in the salt solution for half an hour.
Prediction: I predict that the solution with the more salt percentage in will make the chips loose weight due to osmosis. As there will be more water in the chip than in the highest percentage of salt solution. This will make the cells move from the highest concentration (the chip) to the lower concentration (the salt solution) this will make the chips lighter and smaller.
I think that the best salt solution to use would be 3% due to the fact that there is not too much water in either the chip or salt solution so the cells will not move too much. Also there is enough salt to preserve the chips in a chip shop for most of the day.
Method: 1) Gather all equipment needed, so that is; salt, water, scales, thermometer and 6 beakers measuring at 100ml.
2) Fill up all 6 beakers with the same amount of water all at the same temperature (roughly room temperature – 22`C)
3) Weigh out the salt. First at 1g, then 3g, then 5g, then 7g and finally 9g, leaving one beaker free no salt to be added.
4) Mix the salt solution around so that the salt dissolves.
5) Cut the potatoes to 8cm long.
6) Place two of the cut potatoes and place on the scale take the measurement. Add into the beaker with no salt.
7) Repeat number six this time for the beakers with 1g of salt, 3g of salt, 5g of salt, 7g of salt and 9g of salt.
8) Leave them for 30 minutes.
9) Take out the potatoes weigh them again like in step six.
10) Record the difference in weight.
Results:
Conclusion: My prediction was correct, as I thought that the salt solution with 3g of salt would be best to use to make sure that the chips are preserved and do not loose any weight. I know this because in my results table it shows that the average for 3g of salt is 0. This means that osmosis has not taken place due to there being a reasonable balance of water in both the salt solution and the two potatoes. So for the local chip shop I would recommend that they place their potatoes in a 3 percent salt solution as the chips will not loose weight nor will they go brown as 3 percent of salt would be enough to preserve the potato for the rest of the day.
Evaluation: My experiment went according to plan, the thing I would change if I were to do this experiment again then I would make sure that I do preliminary tests changing the temperature of the water and leaving the salt solution at 3 percent.
The salt solution with 7g of salt is the odd result as it has an average of –1.5333333333 where 9g of salt has an average weight change in the potatoes used of –1g.
My results are conclusive as it was expected that the solutions with low salt would mean that the cells transfer from the solution into the potato. Where as with the solutions with a higher percentage of salt the cells move out of the potato into the water, therefore the potato looses weight.
