highly unlikely, there could be the possibility that two different rulers have slightly different measurement divisions. The experiment should be timed exactly and using the same stopwatch and having the same person operating the stopwatch each time. The time that the experiment is conducted over must be kept the same each time for the same reasons as the volume of distilled water. The same electronic balance should be used to get beginning and end masses of the potato cores in case of variations in measurements again.
Controlling the conditions;
There are some controls I can use during this investigation such as not leaving the test tubes containing the experiment near to any radiators or in the direct sunlight in case of evaporation. The test tubes will have to be kept away from anything else to avoid the possibility of contaminations that could have an adverse effect on the results. There could be some things that I will be unable to control such as spillages from the test tubes or different batches of distilled water having to be used.
Equipment list;
For this investigation there is a lot of equipment that I will need to use, I have listed it below:
- A potato
- A Potato corer
- A knife
- A cutting tile
- Five clean test tubes
- A test tube rack
- An electronic balance
- 250 ml of distilled water
- A ruler
- A clock or stopwatch
- A biology laboratory
- A measuring cylinder
The method;
To begin with, I will have to take several cores, using the corer, from the potato and cut them to their appropriate lengths. I will then have to take the staring mass of them using the electronic balance. Then the cores will be placed in the test tubes, 1 core per tube. Using a measuring cylinder, measure out 50ml of distilled water into each test tube containing the potato cores. The tubes and cores now have to be left for 10 minute, timed with a clock or stopwatch. When ten minutes has passed, the cores are removed from their solutions and carefully dried off. They then have to be replaced on the electronic balance and he finishing masses taken and recorded. Using the start and end masses, the percentage increase or decrease of the surface area has to be calculated. To get some more sets of results for comparison, the experiment should be repeated up to five times after the initial time.
The results;
Preliminary test;
Before being placed in the distilled water:
After 10 minutes in the distilled water;
Quick reflection; as you can see, the smaller cores of potato have had the greatest increase in mass, as I said would happen in my prediction
First repetition:
Before being placed in distilled water:
After 10 minutes in distilled water:
Quick reflection on first repetition:
As it is quite clear to see, there is an anomalous result in the above table for the 2.25 cm core. The large percentage changes have appeared too early in this experiment. There a re a number of reasons for these results but the two obvious ones are my calculations and the set up of the actual experiment.
Second repetition;
Before being placed in distilled water:
After 10 minutes in distilled water:
Quick reflection of second repetition;
As you can well see, there is one clearly anomalous result in this experiment, the 0.5 cm core. It is well over twice as big as either of the previous two of the same size so I must have done something wrong during the actual testing but I can’t be sure what it was.
Third repetition;
Before 10 minutes in distilled water:
After 10 minutes in distilled water:
Quick reflection on third repetition:
I think that out of all of my repetitions, this one was the best and most accurate. This is because there aren’t any anomalous results as before and the differences aren’t too erratic or seemingly stupid.
Evaluation:
Overall, I think that this investigation was conducted well. The basic aim of the investigation was carried out and several repetitions provided me with reliable evidence to use. Despite there being a few anomalous results, there were enough good results to use to draw a conclusion from it all. I think that I carried out the experiments quite well, sticking to the outlines in the ‘fair testing’ section of this write up. The only problem that I can think of with this investigation was finding somewhere to position it away from direct light, because there were a lot of windows nearby and the sunlight was quite intense, this may have caused evaporation on some of the experiments and so causing the anomalous results.
Conclusion:
As stated in my prediction, the smaller cores have encountered the most percentage growth because of the concentration gradients of the starch and the water. The results from the tables were placed onto the graphs and if a pattern seems to be emerging then it would be possible to estimate results for different sized cores than I have used. The results on the graph are just as accurate as the ones in the table because they are the same so there is no room for any criticism there.
