Introduction
This is an investigation into the water movement, through a partially permeable concentration.
In this experiment Im going to use the range of sucrose solutions 0,0 (distilled water, 0,2 0,4 0,6 0,8 1,0. These shall be provided to us when we do the experiment. In future experiments I may choose different sucrose concentrations, it all depends on the results that I get back at the end of this experiment. I will not need to worry about how to make these solutions as they will all be provided.
Hypothesis
I predict that the higher the concentration solution the more water the potato loses to osmosis. I think that it will decrease in both length and weight; I also think that the lower the concentration of the sucrose solution the more water the potato chip shall gain via osmosis, I think that this potato chip shall ‘turgid’. Being heaver, and slightly longer then it was before entering this solution.
Apparatus
- One potato
- A white tile (used for cutting)
- Cork borer
- Razor Blade
- Pen and paper
- Ruler
- Electronic Balance
- Six white labels
- Six Test tubes
- Two test tube racks
- Paper towels
Method
First of all a potato was taken, and cut by the cork borer, to make enough pieces to put in each test tube. The ends were trimmed to leave just the inside of the potato. They were all cut in half so they were roughly the same size. Special care was taken here to make sure we didn’t cut ourselves. They were then measured with the electronic balance; a ruler was then taken and there lengths were roughly taken. Weights and lengths were then recorded.
Six test tubes were labelled with the following, 0.0 (distilled water), 0.2, 0.4, 0.6, 0.8, 1, 0. Small amounts of each of the given solutions were poured into each test tube. Enough was poured so that when a potato chip was put in the solution it was covered completely. The potato chips were allowed to stand for half an hour. After that each potato chip was taken out and gently patted with a paper towel to remove excess water. They were then weighed again with the electronic balance, and then measured with the ruler. Weights and lengths were recorded.
A Similar Diagram to What Happened in this Experiment
Results
Here is a table to show the weights and lengths I got on my first experiment into osmosis.
A Graph to Show Why I did 3molar
Even though this graph is not from my results you can see that, between the sucrose concentrations 2(m), and 4(m) the line drastically changes. In a follow up experiment if I did 3(m) as a sucrose solution it would show more accurately what the concentration of the potato would be.
Conclusion
Even though this graph is inaccurate, in my first experiment I did not take such care in measuring and weighing the potato chips. You can still see that in-between 0.2 molar and 0.4 molar this is where the potato chips concentration changes drastically. If in my final experiment I choose 0.3 as a concentration of sucrose solution I could look at this more closely and see exactly where the potato’s concentration changes.
From my first experiment I have learnt that the higher the concentration solution the more water the potato loses to osmosis. Making it plasmoylised and decrease In both weight and length.
Evaluation
From this experiment I understood osmosis, a lot better. I thought though for my final experiment that I should make some changes to the variables to make it a fairer test. For example in this experiment I left them for 30minutes. I got pretty good results but I think that I possibly could get better.
So in my final experiment think that I might leave them for longer maybe around an hour to give osmosis more of a chance to happen.
I think that this experiment was accurate but for my final experiment I would like to improve it. I am quite confident with my conclusion as I think that it makes sense.
If I was to look further into osmosis I think that I might do the same experiment a lot more, and in different paces as well, to see if the temperature varies. Weather osmosis works better in hot conditions rather then cold ones.
In my next experiment again to keep it precise I think I might use an electronic balance that measures to 0.01(g). Making sure that the electronic balance is put back to zero each time. I also think that to be sure that my final experiment, my results are reliable Ill do it twice with two of each sucrose solution.
My Final Experiment into Osmosis
Hypothesis
I predict that the higher the sucrose, (above a certain level) more osmosis will take place. The higher the concentration of the solution the more water will diffuse into the potato. The lower the concentration of the sucrose solution the more water will diffuse out of the potato.
Apparatus
For this experiment I am going to use accurate equipment to make my external variable as ranged as possible.
- 10 test tubes (final experiment shall be done twice to be more accurate)
- 1 potato
- Cork borer
- White tile (used for cutting)
- Papers towels
- Razor blade with tile
- thermometer
- ruler
- electronic balance
- measuring cylinder
- pen with paper
Method
One potato was taken, and with the cork borer several pieces of the same size potato were cut. They were measured with a ruler, and then the tops of the skin at the edge were cut to leave a cleanly cut potato. Special care was taken here to insure that we did not cut our self’s using the razor blades. All potato slices were to be made 2cm to make it a fairer and more accurate experiment.
Was measured they were then weighed, by the electronic balance, there weights ranged from 1.09g – 1.26g.
Sucrose solutions were given out and all ready on the benches these included 0, 0 (distilled water) 0,2, 0,4, 0,6, 0,8 1,0. I wanted to do five solutions, but I wanted to include 0,3 as one because in my previous experiment if drawn as a graph 0,3 molar is around the point where water changes from diffusing into the potato to out of the potato.
So I thought that this would be a good solution to look at. All solutions were all ready made, so to make it fair a poured 10ml of each sucrose solution that I was going to use into a clean test tube. I wanted to do it twice to make it a more accurate test so I had 2 lots of 10ml sucrose solution for 0,0, 0,2, 0,3 0,4 0,6. 0,3 molar was not a given solution so to make this I did 5ml of 0,6 with 5ml of H2O (water). Again I did this twice to be more accurate. Each test tube was labelled with the sucrose solution on the outside.
Before I put the potato chips in I took a measurement of all the test tubes to see if they varied at all. I then added one potato chip to each solution, and left them for over an hour.
Once the potato chips had been left for over an hour I returned to measure the potato chips and take some results.
Each potato chip was taken from the beaker and was placed on a paper towel to lose access water. Care was taken to make sure that no water was actually removed from the chip. Each potato chip was weighed again on the electronic balance, and then measured again with the ruler. Results were recorded and written down.
Results
Here is a table to show my results in my final experiment:
In this table of results I have chosen to include more averages and also the temperature of the water before and after adding the potatoes.
Here is a Graph to show an experiment on osmosis
Conclusion
From the graph shown above you can see that the generally the lower the sucrose solution concentration the higher the change in mass of the potato, which means that more water is moving into the potato, (water moving from a low concentration to a high one). The graph also shows that the higher the sucrose solution the lower mass of the potato. The slope of the graphs shows what the potato chips would have been like.
The lower sucrose solutions would have had a more turgid potato chip, and the higher the sucrose solution would have made the potato chip more plasmoylised.
My hypothesis is actually quite similar to my results; I predicted that the higher the sucrose solution concentration the more water will diffuse out of the potato. I also said that the lower the sucrose solution concentration the more water will diffuse into the potato making it heavier and more turgid. I thought that in will increase in both weight and length. I don’t think that I would have been so sure of this in my hypothesis if I hadn’t done little experiment previously in lessons and looked at what would have happened.
My graph also tells me, because I did 0, 3 molar this is around where the potato changes from water moving into it, too water moving out of it. This can be proved by looking at two different potato chips one from a high sucrose solution and another from a low one, one potato should be tugor, and the other plasmoylised.
If I had to do this experiment in more detail, again I think that I would do the same concentration of sucrose solutions as I think that they are a good range. I think that if I could change the experiment, I would do lots of the same solution, putting each of them in different spaces. For example, one outside, one inside, too see if osmosis worked well in hotter or colder temperatures.
I did check the temperature in my experiment but the temperatures were extremely constant. This was good for my experiment as I wanted a fair test. Extremely different temperatures in my experiment would have maybe made the osmosis in one test tube work better then in another.
I would have also left some for longer and some for shorter periods of time, as in my two experiments I found that half an hour wasn’t long enough for osmosis to properly and I don’t know what the right time period in a further investigation I would try and find this out. The last thing that I think that I would of done if given a longer amount of time and more resources would have been maybe to add a colour die to the water and sucrose solution to see if a could actually watch osmosis happen.