Investigation into the factors thateffect osmosis in potato cells

3. If the medium has a lower concentration of water than the cell (a very concentrated solution) the cell will lose water by osmosis.

Again water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink.

This is the table to show the process of osmosis from a weak solution to a strong solution.

strong solution

oo osmosis

oo

oo

oo

oo

oo weak solution

* I will need to keep sharp edges in a safe place i.e. not on the edge of a table.

* I will also need to make sure breakable items such as glass test tubes are not near an edge where they could be broken.

* If any thing does break I will need to make sure it is put straight into a bin and not left lying around

* Careful with water so it does not spill and no-body is injured.

The Experiment

For this experiment I will need:

* A potato

* A 7mm cork borer

* Salt solution

* Water

* A scalpel

* Ten test tubes

* A test tube rack

* Weighing scales

* Pipette

* Measuring cylinder

I will also need to decide on a suitable number and range of solution concentrations:

Method

100%

80%

60%

40%

20%

0%

Prepare my salt solutions and test tube rack with test tubes.

Cut out ten tubes of potato using a cork borer and cut them all to one size then weigh each of them.

Measure out the different solutions carefully using the measuring cylinder

Place each of the potato tube into a test tube of salt solution and leave it for 30 mins this should give enough time for osmosis to take place.

After 30 mins I will take them out of the solution, re-weigh them and record the difference in table and a graph.

Prediction

I think that in the 100, 80 and 60% solutions the potato will lose weight and shrink because there is a net flow of water molecules to the less concentrated solutions, but in the 40, 20 and 10% solutions the potato will gain weight and swell because these are the more diluted solutions so the net flow would be to these ones.

If I was to do a solution, which didn't change the weight at all, I think it would most likely be around 20%, depending on the concentration of the potato, it would have to be a neutral balance between the salt solution and the concentration of the potato. So if the two had the same concentration osmosis would not have to take place at all. I think that the stronger the solution the more osmosis would take place and it would make the potato smaller, because of its attempt to even out the solutions. So, if the solution was 0% the potato would grow because it would take on water because it is slightly salty itself and would want to even out.

I also think that the most difference will occur with the 100% salt solution because

If this for some reason doesn't happen then either my prediction is wrong or the experiment I have done was imprecise.

I will do this 3 times because this should make sure if one set of results is very odd I will use the one which seem to be more likely.

Results

concentration

start weight

end weight

concentration

difference

00%

2.31g

.98g

00%

33g

80%

2.33g

2.01g

80%

32g

60%

2.30g

2.02g

60%

28g

40%

2.30g

2.52g

40%

22g

20%

2.32g

2.38g

20%

6g

0%

2.30g

2.51g

0%

21g

concentration

start weight

end weight

concentration

difference

00%

2.30g

.97g

00%

33g

80%

2.31g

2.00g

80%

31g

60%

2.33g

2.03g

60%

30g

40%

2.30g

2.51g

40%

21g

20%

2.32g

2.39g

20%

7g

0%

2.30g

2.51g

0%

21g

Conclusion

The results I have found justify my prediction which means that these are the ways in which osmosis works in potato cells

i.e. the potato gains weight with a low concentration and loses weight if there is a high concentration solution.

My results do follow this pattern another pattern is the difference between the start and end weight for the high concentration solutions is around 30g but in the low concentration is only about 20g I have constructed my graphs and they show this too.

I think this experiment is a good way to test the results of osmosis provided it is done correctly because it is accurate and safe. It gave precise enough results to construct graphs and diagrams which provide suitable information on the topic.

Both of the graphs I constructed show roughly the same results showing that the experiment was done quite accurately.

If I were to do other experiments I could for example keep on doing this experiment until I found a solution which had no movement of water this would give me the concentration of NaCl in the potato.