I am intending in this experiment to five different concentrations of salt ranging from 0-4 and repeat each one of these twice to give me more accurate results, which I can then take an average from. I will not use 5 as one of my salt concentrations because we already used this as part of the preliminary experiment. I will cut five evenly sized and weighted disc of potatoes out and weigh them then insert them into the right salt concentrations. I will leave this experiment and come back in 25 minutes then take out the potato discs record there new weight and put this in a table. When I have all my results in I will see how much the potato increased or decreased in weight by looking at this I will be able to see if my prediction is correct.
Variables that may affect the experiment (rate of osmosis) –
• Concentration of Salt Solution
• Size of the potato
• Temperature of surroundings
• Time
I will need to make some precautions for my experiment to make sure that it is fair and I don’t get to many anomalous results. I need to make sure I remove all the potato peel of the discs because this will affect how much can penetrate through. Also I need to make sure that I blot dry them before reweighing otherwise sum access water may be on them making them seem heavier.
Experiment A
Experiment B
Average
Waited for 25 minutes before removing potato. 5 potato discs in each test tube.
= Anomalous result
Analysis
My results did agree with my prediction because it was accurate. From my graph I can see that as the salt concentration got higher the potatoes started losing more weight I can tell this by the shape of the graph. My graph shows that at 0 concentration of salt the potato gain a weight of 10 % and that as the concentration got higher to 1, 2, 3 and 4 the potatoes where losing more weight quicker the weight of the potato started of at a gain of 10 % and at a concentration of 4 dropped to – 20.4% so there is a big difference between start and finish.
Conclusion
As described in my predication I can see my results ended up as they did because movement of substances takes place through the cell membrane, which separates the different substances in the cell from its surroundings. This type of membrane allows small molecules such as water to pass through it, but it denies entry to salt so there is no way the potato can get any heavier. The salt erodes at the potato instead making it lighter.
Evaluation
There was one anomalous result in my table and that was in experiment ‘A’ where on the ‘1’ concentration of salt the potato got heavier when it should of got lighter this may have been because we might not have blotted it probably before we weighed it again. This anomalous result does not matter because on the experiment ‘B’ we got an accurate result to use as our average.
The experiment could have been improved by doing a bigger variety of salt concentrations, left them all for longer and done more than two repeats. These points need to improved to get much more accurate results that will make the test a lot fairer. If I did improve these few things my prediction and conclusion would still be correct but my results would just be a lot more accurate.
