The reason for my prediction is based on a preliminary test I carried out before hand. This is how it turned out:
← Petri dish, split into three sections 1, 2 and 3.
0m pure water:
In this experiment is shows that each potato, after each given time, they all gained mass, instead of loosing it. This means that the water from the beaker transferred into the potato, making it gain mass
1m salt solution:
After doing this second experiment it showed that even after 15 minutes each potato gained mass, but they were all the same weighed after the final mass, loosing the same change in mass.
Planning:
The plan for the preliminary test is to see what happens after putting three potato chips into 0m pure water and 1m pure water. This will show us how concentrated it was and what the affect was.
For each of my experiments I will have to find out the % change in mass. To do this I will gather my change in mass, divide by the original mass and x by 100.
I.e.
0.03 (change in mass)
1.10 (original mass) x 100
= 2.72
Method:
During the experiment certain things have to happen in order for the investigation to work.
First of all I will have to cut the potato chip. Each chip will have to be the same size for a fair test (2.5cm)
To make it easier on the Petri dish I will mark 1, 2 and 3 for each chip to be placed in the certain earlier.
There has to be an original mass so after each chip has been in the solution for the desired time I can compare mass.
Example: the original mass of 0m is 0.905. After being in the solution for 5 minutes the final mass is 0.930. From that I can now work out the change in mass and the % change in mass
this will again happen after 10 and 15 minutes
I will start off at 0m then go up to 0.25m, then to 0.5m and finishing at 0.75m
after the chip has been in the solution for the correct time it has to be dried. Then will be weighed again for the final mass (explained above, underlined)
At the end of the experiment which will roughly take place over two lessons I will collect the results which will be shown later
Apparatus:
The apparatus needed for this experiment will be:
- Stop watch, to time 5, 10 and 15 minutes.
- 3 potato chips (all measuring 2.5cm)
- Petri dish
- 0m, 0.25m, 0.5m, 0.75m, 1m salt solution.
- Balance
- Measuring cylinder
- Salt
- Borer, knife
.
Fair test:
To make my experiment a fair test I will keep these things the same:
- Size, measurement of potato
- Brand of potato
- Time in solution (5, 10 and 15 minutes)
The only thing I can change is the strength of the salt solution.
Results:
After completing for experiment my results are as follows:
0m
0.25m
0.5m
0.75m
1m
The anomalous results are shown in red and are not included on my graph.
Averages:
0m = 7.68
0.25m = -3.523 these averages will be shown on my graph.
0.5m = -9.09
0.75m = -15.35
1m = -16.27
Analysis:
From my results it shows that the prediction I made was correct. The more concentration the less mass gained. Concentrated)
On my graph I have circled where the isotonic point is.
Also on my graph, I did not do a line of best fit. I plotted accurate averages onto the graph and used it to make a curve going down the paper
From my graph you can see that my prediction was right and that the more concentration there was (strength in molars) the more weight that the potato lost.
Evaluation:
I feel that the experiment worked because it supports my prediction well and is similar to my preliminary test.
I feel the experiment was 70% accurate but wasn’t that reliable.
This is because after leaving the potato in the certain amount of salt solution, after the time was up it was often difficult to retrieve the potato chip from the water. So it was in the solution for a fraction more time, maybe varying my results.
However I do feel that most factors were accurate such as:
- The amount of salt solution used. Half a Petri dish was filled for each experiment.
- Timing was accurate, however as I mentioned some of the chips were left for a few extra tenths of a second. But overall each timing was correct.
Factors I feel that were not as accurate as I would have liked is that the potato chips may not have all been the same size. We measured them out at 2.5cm each but 1 or 2 might have been either a little bit bigger or even a little bit smaller. we did however use the correct tools to cut and measure the chips so the measurements wouldn’t of been that out.
Some results came back anomalous, instead of repeating it, we simply took the anomalous result out, and found the average by adding up the two other % changes in mass, and dividing it by 2. If in 1 experiment there wasn’t an anomalous result we would have added up all 3 % changes and then divided by 3.
Nothing during the experiment happened that would have been of any use or advantage/disadvantage. Maybe except that on a few of our results they came back anomalous, but we did not know this until the experiment was over and new weights were given and the % change in mass was found.
If we were to do another experiment using a potato chip we could maybe change the length of time, or change how much salt solution we actually used in each experiment.