An experiment to show the movement of water into and out of plant cells to discover the concentration of the cytoplasm

If however it is a strong solution e.g. salt the opposite will happen the potato will shrink because water leaves its cells due to osmosis happening. The water will get pushed out by the salt solution this will happen until the water and the salt solution are equal meaning that it has gone lighter and has lost weight. Making it feel flaccid.

Procedure (Method)

I am going to leave a potato cell in a petri dish for 24 hours in 5 solutions, 4 of those solutions are going to be salt solutions ranging from strong to weaker solutions of salt. The other petri dish is going to contain pure water.

* Firstly I collected the equipment that was required and set it up.

* Secondly I then used a cork borer to cut out 5 potato cylinders , I achieved this by sticking it actually in to the potato and then poked it out using a pencil.

* Thirdly I then measured the length and diameter and recorded it on a some paper. If it was to long I cut it down accurately using a plastic knife. weighed the potato's and recorded it.

* Fourthly after I then proceeded on by weighing the potato on a electric scale ad again noted down the outcome.

* Fifthly I then labelled the petri dishes 1 molar, 0.75 molar, 0.5 molar, 0.25 molar and distilled water (0 molar).

* Fifthly after I recorded everything I then put the potatoes in the petri dish and carefully measured the amount of salt solution that went in to 4 of the petri dishes and the distilled water dish. I put an equal amount of 20ml in each of the dishes.

* Lastly I left my petri dishes in a safe place for 24 hours and came back the following afternoon to observe what had happened.

Equipment

5 Petri dishes 1 pencil

Cork Borer 1 ruler

Plastic knife 1 Paper towel

measuring cylinder

Balance electronic scale

Potato

Fair Test

Making it a fair test plays a big part if it isn't fair it leads to a set of anomalous results. First of all I had to use the same potato because if I used a different brand of potatoes the results would come out wrong.

I also think that the potato should be fully covered in the solution because the potato should be fully submerged, by having total contact with the solution.

When I am using the balance I will make sure that before putting the potato on it the balance is reading 0. This is so I don't get a false reading which could disrupt my results a lot.

Another important facture in making it a fair test is getting the exact measurements at the end even measuring it to the nearest millimetre will help a great deal as we try to find out about osmosis. If all goes well it should lead to a god set of results and a decent conclusion.

Safety

Safety is an important aspect in every experiment, even if the experiment seems to be very harmless. And that is why we take this into consideration, no matter what. We will be using a Roller Borer, which could injure someone if it's not handled properly. And we will also be careful that the solutions don't get into our bodies internally, just in case, because we are not fully aware of the damage it could do to us. But apart from that there isn't nothing else we should really be cautious of that does physical damage.

Key Variables

To create a fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. I have chosen to vary the concentration of the salt solution. This will give me a varied set of results from which I hope to make a decent conclusion. If all of the variables are kept the same it would mean it would not be a fair test. For instance if one of the potato's was 1cm longer the surface area of the potato would be larger and there would therefore be more space for osmosis to occur. The variables I will be changing is the strength of the salt solution placed in each Petri dish. They will have 1 molar, 0.75 molar, 0.5 molar ,0.25 molar and 0 molar (distilled water). In doing this I get a good idea what osmosis does to strong and weak solutions.

Results Table

Here is my results table I have made it easier to show by the differences from before and after along with a simple calculation which will explain all of this.

Length Results

Solution

Length Before (mm)

Length After

Calculation

Difference

Percentage (%)

molar

50

42

50-42

-8

6

0.75

50

46

50-46

-4

8

0.5

50

48

50-48

-2

4

0.25

50

47

50-47

-3

6

0

50

52

52-50

+2

-4

I found out that all lengths had decreased up to 8m. 0 molar had actually increased in lengths this can be explained simply because the potato cylinders have swelled up this is because water has entered their cells by osmosis causing it to become turgid. This all can be backed up by my scientific knowledge. The reason why salt solutions have shrunk in size is because water leaves their cells due to osmosis, this again can be backed up in my scientific knowledge.

Mass Results

Solution

Mass Before (g)

Mass After

Calculation

Difference

Percentage (%)

molar

3.20

2.30

3.20-2.30

-1

28

0.75

3.55

2.70

3.55-2.70

-0.85

23

0.5

3.35

2.35

3.35-2.35

-1

29

0.25

3.75

2.50

3.75-2.50

-1.25

33

0

3.15

3.30

3.30-3.15

+0.15

-4

The Mass had increased for 0 molar by 0.15g this is as similar as the reason for length. It increased because when the water concentration is lower in the tissue, the water will go inside the tissue of the potato, and the potato will gain weight. The weight for all salt solutions has increased by up to 1.25 this is because potato has shrunk from earlier (length results) because water leaves its cells due to osmosis happening. The water will get pushed out by the salt solution this will happen until the water and the salt solution are equal meaning that it has gone lighter and has lost weight. This can also make it feel flaccid.

Diameter Results

Solution

Diameter Before (mm)

Diameter After

Calculation

Difference

Percentage

(%)

molar

8

4

8-4

-4

50

0.75

8

4

8-4

-4

50

0.5

6

6

6-6

0

0

0.25

6

3

6-3

-3

50

0

6

7

7-6

+1

6

Again everything increased for 0 molar, it went up by 1mm due to the fact that water has entered the cells making it swell up. I have begun to see a patter where everything has concerned with the repeat of O molar increasing and the salt solutions decreasing. With the diameter I have come across an error where the diameter for 0.5 nothing has happened but for 0.25 there is a 3mm difference. This is an anomalous result because 0.25 molar is weaker than 0.5 meaning something should have happened 0.5.

Conclusion

I have found out that I was right in my predictions all potatoes did go lighter . Also on some the diameter stayed the same and on some it shrunk .my predictions for weight were different. Underneath I have found out the differences of what happened to each solution of salt.

molar

With 1 molar the weight of the potato dropped by 1.10g from its previous mass of 3.20g , the length had been effected by a 8mm difference this is because the salt solution broke down the potato pushing out quiet a lot of the water . The diameter had dropped by half to 4mm.

0.75 molar

0.75 molar had dropped by 1.25g more than 1molar the size didn't shrink by a greater deal it went down by 3mm to 47mm to do with how strong the salt solution is since it is weaker than 1molar it wouldn't push a much water out. The diameter dropped by half to 3mm.

0.5 molar

This was in the middle of the solutions it wasn't to strong or to weak . It lost 1.0g of weight form its previous weight this is kind of what i expected because since it is in the middle it would lose roughly the middle number the other solutions have. The length decreased by 2mm which is again in the middle of the solutions. The diameter stayed the same al the way through because of the solution not be strong enough to push out as much water as 1 or 0.75 molar.

0.25 molar

The salt solution in 0.25 molar will hardly eve move any water out because of being so weak. The weight went down by O.85g to 2.70g this was less than all the other salt solutions. Even though it wasn't as strong as 0.5 the length had dropped more than O.25 down from 50mm to 46mm. The diameter dropped by half to 4mm.

0 molar

This was just distilled water, instead of everything going down everything went up the mass went by 1.5g this shows that the water in the beaker had moved in making it turgid. The length had also increased it went up by 2mm and the diameter went up to 7mm, this is also because of the added water that the potato had soaked in .All of this can be explained by the distilled water which was a high water concentration moved across to the semi permeable membrane in to the cell (low water concentration) making the cell swell and become turgid.

Analysis

I have analysed my results carefully and come have concluded what I have did. From my results I have gained knowledge and I have found out the anomalous results. By mass, length and diameter. When I first done the experiment I had measured everything to the right length and weighed accurately. All salt solutions had changed considerably every salt solution except 0 molar all became Flaccid and 0 molar went turgid even harder than it was previously. This was because when the potato was placed in distilled water (high water concentration) water will move across the semi-permeable membrane into the cell (lower water concentration) by osmosis, making the cell swell. This is why it has now become turgid.

For all the other salt solutions it can be explained why they went soft and became smaller in length, mass and diameter. Since all the other solutions were placed in a low water concentration the opposite happened water would move out of the cell and in to the solution. In some cases the cell membrane breaks away from the cell. The cell is now refers to as plasmolysed. This is why they have decreased in mass, length and diameter.

There will be a point where osmosis completely stopped when the concentrations of water and outside the potato become equal showing no change in mass, length and diameter.

I have also spotted a trend during the experiment if you increased the salt concentration this would lead to decrease mass. This was up to a 1.25g decrease. The same trend goes for length and diameter. O molar is the only solution that will increase in length.

The anomalous results I found were for my mass table I found out that 0.5 decreased mass more than 0.75 which in theory shouldn't happen. The outcome should of had 1 molar losing most but had 0.25 molar lose the most mass. I think this might of happen because I might of poured to much solution in to it making the test have an unfair advantage.

I had another anomalous result involving salt solution 0.5 molar, the diameter of it didn't decrease as it should of done, even solution 0.25 molar which is weaker than it did by 2mm leaving another anomalous result. Amongst all of this 1 molar did decrease but less than 0.75, which decreased 1mm more than 1 molar. This scientifically shouldn't of occurred but is most likely to inaccurate measuring of the molars.

The length section had 1 anomalous result amongst it again 0.5 molar plays a part in it, 0.75 is supposed to decrease length more but ended up decreasing less.

After looking at all the wrong results I have concluded that 0.5 molar was the one which had the problems in each section I have covered, this can easily be because of inaccurate measurement been taken or because of solutions being poured in to much or even too less.

To show and express more in dept on changes in patter to my experiments I have added graphs to show more of an understanding. The graphs I have done are for length, diameter and mass.

Evaluation

We followed the plan correctly, I believe I have gained a reasonable amount of accurate and sufficient results to conclude the experiment, some results did come out anomalous. Even with all the anomalies results I think the outcome of my osmosis experiment has been fairly well but could have run better and more accurately which would of gave a even better understanding.

If I was to do the experiment again I would change something which is an important key when learning. I would do the experiment twice to see if the outcome was the same every time. This would help see if I did things wrong and make my experiment more fair test. Also we could investigate in to seeing when osmosis will completely stopped by leaving the potato for a longer period of time. Thus will show more variety of results. Using more types of molar solutions would have helped us obtain better results, and make them more accurate. So that we can make sure the results are totally correct.

To study osmosis to a more deeper extent may be we could of used a variety of potato's or even different foods e.g. carrots. Seeing osmosis in action in different cells would help gain more knowledge. Changing the variables completely instead of using a salt solution we might use a sugar solution to see how the potatoes cells react with different solutions.

To do an experiment without making it fair is useless what is the point of even doing it ? Even when it came to weighing the potato on the balance I wait till it got to 0 otherwise more false results would of come out. I tried to do the experiment with as little faults as possible, I did succeed to a limit with a few anomalous results along the way. I tired to make it fair by not using a different brand of potato's, also by using the same Cork Borer. I tired to measure with as much accuracy as possible and weighing and measuring the potato properly . We could also of used better measuring cylinders because the ones provided were a bit old and had scratches on them so it was hard to see how accurate the solutions were being poured. Also use a more accurate measuring balance because the one we were using was old, some potato's weight might of been effected because water might of been left on by potatoes dripping in the solutions. This could of been avoided if we had enough time to do the experiment so we could of done it 1 potato at a time so instead of wiping about 5 potato's on 1 paper towel but this way would be very time consuming. We could of used a test tube instead of a petri dish this would help by observing better. This wasn't possible in our case because supplies were limited.

After all I have learnt in this experiment I think that I have learnt enough to carry out the experiment again and make it better with out the faults the first time.