Osmosis- Plan Cont
Making the test fair will be very important in this experiment. If the results are not accurate we could be lead to the wrong conclusions. We will be trying to make the solutions as accurate as possible by measuring the ratios properly. Also to make the test fair we will be using a sensitive balance before and after the experiment so that we have to measurement to the nearest hundredth of a gram. Also, one of the most important things to think about when doing this experiment is making sure the potatoes are completely covered by the solution. If they are not, the measurements would be very inaccurate. When measuring the mass of the potatoes I will also be making sure that the balance is on zero, this is so we don’t have a false reading. To make the test fair we also make sure there is no serious temperature change, as this could seriously affect the end result, especially if some of the results have not experienced this change in temperature. We will also take into account cracks in equipment.
Safety is also an important part of this experiment. We must take notice that we will be using a sharp knife in the experiment, which could serious harm someone if it is not used properly. We must also make sure that no solution gets inside us, as we don’t know what damage it could do. That is the only real danger.
(Osmosis is the passing of water molecules from a weaker solution into a stronger solution, through a partially permeable membrane. [Taken from BBC.CO.UK]) This means that when the salt solution is less concentrated than inside the potato, the potato will lose weight. The opposite occurs when the solution of the salt is stronger. If both the concentrations are the same then no osmosis will occur. I believe the weaker solutions (4:10 5:10) will make the potato gain the most weight because they have a higher concentration of water. And the stronger solutions (1:1, 9:10) will make the potato lose weight as the water is leaving the potato.
Osmosis- Obtaining Evidence
After this experiment, I had to dry the potatoes first, so that the water around the potatoes didn’t affect the weight, and so that the results turn out more accurate. I also took all of the potatoes out quickly and measured them. This was to make sure the experiment was as fair as it possibly could be. I noticed that the change in weight was to small to be seen just by looking at the potatoes. You had to measure them with a sensitive balance to get the readings properly.
Below are the results of my experiment. They are written in a table and on a graph on a separate page.
This Graph shows Changes Before and after experiment.
This Graph shows how many grams each Concentration of the solution changes by.
All the results were repeated so that we had two sets to ensure we had done the experiment correctly. Unfortunately some of the results on the second test were inaccurate.
Osmosis- Analysis
As you can see on my graph I have used two different colours to show the mass before and after. It shows that when the concentration of salt to water is at its highest osmosis occurs so that the potato loses water. When you get to the top end of the graph the concentration of salt is lower so the potatoes gain weight. This is because there is more water in the solution to move to the potato pieces.
If I had done this as a line graph I would have used my second table of results, as this would have shown me how it would change more easily. There were no mathematical relationships that I noticed as the changes in weight gain were not exact.
In this experiment I have collected enough information to support my prediction. It was also exact enough to prove what I wrote. By looking at the results and the graph you can see that only one or two results are out of line. None of these results show my prediction to be wrong and all the measurements have been taken with reasonable accuracy. This experiment also shows the phrase (Osmosis is the passing of water molecules from a weaker solution into a stronger solution, through a partially permeable membrane. [Taken from BBC.CO.UK]) To be correct.
Osmosis- Evaluation
In this experiment I followed the plan correctly and made all the precautions that were necessary to make the experiment accurate. I also believe that we gave enough information that was accurate enough to prove my prediction. To make the experiment better I could have repeated the results more times. It would also be better if we had done each of the concentrations separately instead of all at the same time. This would have reduced the time between moving the potatoes from the test tubes to the balance. It also would be better if there were more people to help do the experiment, as then the tasks could be split up and we wouldn’t all be rushing to get things completed.
Even though we didn’t do these things, I still got the same results as I had predicted apart from one or two. The only result I did not expect was on my second test on the ratio of 7:10. This result was strange because a lot of weight was gained. I think this may have been a flaw in the experiment, as it did not match with the other test.
To find out extra information I could use the salt solution and find out what the ratio is after the experiment. Overall I am pleased with my results.
