The preliminary results show that the higher concentration of sugar in the water solution the less weight the potatoes slice gained.
Hypothesis: Whether the potato slices loose or gain weight will depend on the concentration of sugar. I believe and my preliminary results support this, that the higher the sugar solution the potato slices are left in, the less their mass would increase by. This is because the higher water concentration would be in the potato, rather than the sugar solution, which would mean that at a certain concentration of sugar solution, the potatoes were in, would loose weight, rather than gain it, as the lower water concentration would be in the solution the potato slices are put in so water would travel out of the potato into the sugar solution.
I would expect to gain the following results:
Equipment:
· Cutting tile Knife Potatoes Tissue paper Scales Cork borer Test tube holder five test tubes Sugar solutions
Fair Test: To make this a fair test I must make sure that only one factor in the experiments is changed – that’s the concentration of sugar, everything else has to stay the same. Also, when the potato slices are removed from the sugar solution, I’ll dry them with tissue so water on the surface doesn’t affect the weight.
Safety: The potatoes will be cut with quite a sharp scalpel so we must take caution when using it.
Method:
☺ Carefully peal the potato.
☺ Using a bore create a cylinder of potato.
☺ Using a scalper cut this tube into 25 thin discs.
☺ Separate discs from each other.
☺ Sort the disc into five sets of five discs and weigh the mass of each set on a top-pan balance.
☺ Put each set into a labeled test-tube and cover with a different concentrations of sugar solutions.
☺ Leave the samples for 25 minutes.
☺ Take potato discs out and gently dry them with a paper towel without squeezing them.
☺ Re-weight each set.
☺ Repeat experiment using fresh potato discs.
Diagram:
Results: Table 1: showing the mass gain/loss and % change in mass.
Analysis: My hypothesis was correct. The results table shows that the higher concentration of sugar solution the less mass gain for the potato discs. My prediction was also correct in the fact that at 0.8 mol/liter of sugar solution, the potato began to loose it. mass which tells me that the water concentration was higher in the potato than in the solution.
Table 2 contains the average mass before and mass after osmosis takes place. Again it clearly shows that that there is a mass gain until the 0.8 mol/l concentration, where mass is lost. It also shows how the mass gain gets smaller the higher the concentration of sugar and how after and at 0.8 mol/l, the mass loss is quite a small amount but gets larger with higher concentration which suggests that the higher the concentration the bigger the mass difference.
Table 2:
I’ve plotted table 3 onto a line graph. It shows the average % change in mass at all the different sucrose concentration. The graph shows that the change in mass is quite big between 0.4 mol/l and 0.6mol/l as that is the largest difference of 0.4 in concentration of the sucrose concentration. The average % mass change between 0.0 and 0.2 is 33.2% , and between 0.4 and 0.8 is 16.9% which is much smaller, confirming that the higher the concentration the less mass gain. However, at 0.8 the potato looses weight as the concentration of water is higher in the potato that the solution so the change in mass begins to increase, repeating what happened before just in the loss of mass rather than the gain.
Evaluation: I believe my experiment was very successful because it proved my hypothesis right. We also did each experiment twice to make sure the results were reliable. However, I do think there are a few things I could of done to make my results more accurate.
First of all I could make my increase in concentration constant rather than increases of 0.2, 0.4 and 0.3, which would give me more detailed that would allow me to study the changes in mass bit more closely. It would be useful to also do a few more higher concentrations after 1.0 to see whether the change of mass would continue to increase as it does when the concentration gets lower.
I could also have more people in my group so a number of tasks can be carried out at the same time because for example when it comes to removing the potato discs from the solution some groups might stay longer in the solutions than other. Or if some of the potato discs are on the tissue longer than others more water might be absorbed, slightly effecting the results. Also I’d be able to concentrate more on what I was doing instead of rushing to move onto other sets of potato discs so the results we gain are reliable.
