Diagram
Tin Foil
H2O 5% 10% 20% 25%
Salt Salt Salt Salt
Apparatus
- 5 Test Tubes;
- 5 pairs of equal length potato chips;
- Distilled Water;
-
5%, 10%, 20%, 25% salt solutions (with water/ H2O);
- Tin Foil;
- Knife;
- Ruler and Calculator.
A fair Test
Fair testing is an important part of this experiment and so to make sure the experiment is a fair test you need to:
- Have constant values of chip size and length;
- Make sure that the chips are completely covered with the solution;
- Make sure all of the tubes are kept under the same conditions; Temperature etc.
- Put tin foil over the tubes to stop any unwanted substances entering the solution.
What I Will change during this Experiment
The only thing to be changed during the investigation is the concentration of salt to water solution. I.e. my input variable.
Science behind the investigation
Osmosis is the passing of a substance through a semi-permeable membrane into a more concentrated solution.
TURGID- 1.Swollen or distended and no flexibility.
2.Pompous, not flowing easily.
FLACCID- Hanging of wrinkled, not firm.
Every cell is surrounded by a cell membrane, it forms a partial barrier between the contents of the cell and the outside. The cell membrane has tiny holes in it which allow tiny particles to pass through it but not others. This is known as being partially permeable. Permeable means to have substances pass through it.
Results
I believe that the experiment went well as both potato’s produced the same result which meant that the results were quite reliable. The distilled water had the largest effect on the size of the potato. From then on the % change decreased down to –15% from the 20% salt solution
Scientific Explanation For the Results
The higher the concentration of salt solution, the smaller the potato will become. This is because the solution inside the potato at first is stronger than the solution outside and so the exterior solution is passed through the partially permeable membrane into the potato. This therefore causes it to increase in size. As the exterior solution becomes stronger the solution inside the potato is passed through the membrane into the exterior solution. This therefore causes the potato to become smaller in size.
Analysis and Conclusion
This experiment has produced a graph which proves my point which I explained in my prediction. The graph gives me an excellent set of results. In my experiment the potato in the distilled water had gained 21% in length. In the 10% solution the potato stayed the same size and in the 20% solution the potato lost approximately 15% of its size. These prove that the higher the concentration of water in a cell the more it grows.
Evaluation
I think that the experiment went very well, there were no 'odd' results and they produced a good graph. However there were a few areas where there could be improvement. Firstly, when I dried off the excess water on the potato chips after the experiment and before I measured them, I used a paper towel. This might have either taken some water out of the potato or it might of left some excess water on the potato. This part of the experiment is difficult to come up with an accurate and fair method, as other ways could also lead to some slight mistakes.
Also the potato itself was not definitely from the same potato and was not exactly the same size, although I did try to cut them to 3.4cm each.
Another way of improving the results would have been to leave the experiment running longer, this would have enabled me to find the saturation point (when the potato can no longer take in any more water) and dehydration point (when the potato cannot lose any more water) and therefore get a more accurate result.
To use a different substance like sucrose might aid me in drawing a better conclusion and therefore a better evaluation and a better understanding of the theory of osmosis.
Finally, I could extend the experiment to a much better level by looking at the potato chip under a microscope, which would mean I would be able to see the cells in greater detail and draw some more observational results.
