Experiment to investigate how equal masses of potato are effected in different concentrations of 1 molar sucrose soloution.
Tyler Watts.
Experiment to investigate how equal masses of potato are effected in different concentrations of 1molar sucrose soloution.
Aim:
To investigate if osmosis occurs in potatoes, and if so, how it affects potatos of equal mass (2.5g) in different molar solutions of sucrose and water.
Apparatus:
-Cutting tile which will be used to cut the potato on.
-Knife which will be used to peel the potato with and to cut to correct mass.
-Burette which will be used to measure the solutions acurately. -Distilled water to make up solutions as part of the experiment
sucrose to make up part of the experiment
-Potatoes to cut into equal mass and observe what happens to them when left in differing concentrations of sucrose solution.
-Tissue paper which will be used to dry the potatoes after the
-Electronic Balance to weigh the potatoes acuratley. -Cork borer which will be used to cut out potato cylinders. -Boiling tubes to put 20ml of differing solutions into.
Variables:
-Concentration of solute. -Size or surface area of vegatable. -Type of vegatable. -Age of vegatable. -Length of time vegatable is left in solution for.
*The variable used in this experiment has been highlighted in red.
Planning:
Before the planning the experiment, some will Background Information will be needed to find out about osmosis, and other matters related to osmosis, so that a prediction can be made. And to construct a way to make this a fair investigation. Having already done preliminary work on the rate of osmosis on potatoes of the same length when left for differing periods of time this investigation can be seen as a follow up to the previous one. Whereas in the previous experiment the variable was time, this experiment will be kept similar however the potatoes will be kept for the same amount of time but in differing concentrations of sucrose solution. Also, the potatoes have been changed from length to mass as mass will provide a more reliable set of results to analyse.
Background Information:
Osmosis, the net or overall movement of solvent molecules (often water) from a region where they are at a higher concentration to an area where they are at a lower concentration through a partially permeable membrane (sometimes called a selectively permeable or semi-permeable membrane).
Substances often move from an area of higher concentration to an area of lower concentration by diffusion, the result of random particle movement.
In osmosis, two solutions are separated by a membrane that will only let the solvent particles pass through. This means that the solvent continues to move freely along a concentration gradient. However, the other substance involved-the solute-cannot move freely because the particles are too large and cannot pass through the membrane. This means that although there is random movement of the solvent molecules in both directions across the membrane, there will be a net movement of solvent into the area where it is at the lowest concentration-in other words, into the solution containing the highest levels of solute. The easiest way to understand what is going on is to look at a practical demonstration.
We can make a model of the situation using an artificial membrane which is permeable to some molecules-in particular water-and impermeable to others such as glucose. There are many experiments that show the movements of water in these circumstances-one of the simplest is shown in the illustration.
In the demonstration in tube A, the water moves in both directions through the membrane; the flow is greater from the vessel of pure water, however, because the concentration of water is greater there, that is, there are fewer dissolved substances in this solution than in the sugar solution. The level of liquid in the tube of sugar solution will rise until the flow of water from the tube of sugar solution, under the influence of hydrostatic pressure, equals the flow of water into the tube. The hydrostatic pressure needed to establish this equality of flow is called ...
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In the demonstration in tube A, the water moves in both directions through the membrane; the flow is greater from the vessel of pure water, however, because the concentration of water is greater there, that is, there are fewer dissolved substances in this solution than in the sugar solution. The level of liquid in the tube of sugar solution will rise until the flow of water from the tube of sugar solution, under the influence of hydrostatic pressure, equals the flow of water into the tube. The hydrostatic pressure needed to establish this equality of flow is called osmotic pressure.
Partially permeable membranes are often found in living organisms-for example, cell membranes and the membrane lining the shell of an egg-and this is one reason why osmosis is such an important process. We can use it to explain many features of living organisms. In animal cells it is important that as little water as possible moves in or out of the cells. If too much goes in then the cells will swell and burst. If too much leaves the cells they will shrivel and stop functioning. This is plasmolysis. So in animals it is vitally important to maintain the body fluids at the same concentration as the cell contents. All of the complex systems-for example, the kidneys, the adrenal glands, and the role of insulin-which exist in many animals to control the levels of salts and sugars in the body fluids have evolved because of the importance of maintaining a constant body environment to prevent osmotic damage.
In plants the situation is somewhat different because of the cellulose cell wall. Although it is freely permeable and so does not affect what can move into and out of the cell directly, it still has an effect on osmosis. If the cytoplasm of a plant cell contains more solutes than the surrounding fluids water will enter the cell by osmosis-but not indefinitely. The inward pressure of the cell wall on the cytoplasm as it swells builds up until it cancels out the tendency for water molecules to move in by osmosis. At this point the cells are full and rigid, in a state known as turgor. This is the normal and desirable state for plant cells to be in, because it gives the plant support. If the solution surrounding a plant cell contains more solutes than the cytoplasm, then water will leave the plant cell by osmosis and the cell will become plasmolysed. This in turn means the cytoplasm will not be pressing against the cell wall, so the support system of the plant will be lost and it will wilt.
In osmosis, a solvent (often water) moves from a region of low concentration to a region of high concentration through a semi-permeable membrane. Here, water molecules diffuse into the concentrated sugar solution because the water molecules are small enough to move through the membrane.The larger sugar molecules are unable to move through the membrane into the water solution. Osmosis will stop when the two solutions reach equal concentrations on either side of the membrane.
Prediction:
Osmosis is the movement of water molecules across a partially permiable membrane from a region of high water concentraion to a region of low water concentration. Therfore I am able to predict confidentley that there will be a directly proportional outcome in the results obtained. In the pure distilled water I think that the potato pieces will swell causing the cells to become turgid, because of the movement of water molecules into the potato due to the high concentration of water outside the potato as opposed to the lower concentration of water inside the potato. This swelling will cause the mass of the potato to increase. I think this increased mass will gradually decrease (directly proportionally) as the concentration of sucrose in the solution is increaesed. The potatoes at the other end of the scale, in the 1molar sucrose solution, I think will shrink, causing the cells to become plasmolysed and resultingly decrease in mass due to the fact that there will be a higher water concentration inside the potato than outside in the sucrose solution (1 molar) causing there to be a greater net movement of water molecules from the potato to the outside solution than vice versa. This loss of water is what I expect to make the potatoes decrease in mass. Because the glucose will be unable to travel from the solution through the partially permiable membrane, (because they are too big) then the higher the concentration of solution and the smaller the mass of the potato should resultingly be. The more water that does enter the potato the more they will swell and the more turdgid the cells will become. As the potatoes will be left in solutions ranging from pure distilled water to 1 molar sucrose solution then I think the potatoes masses will range from one extreme to the other and will gradually change as the concentration is increased/ decreased. This is the reasoning for my prediction that results will be directly proportional.
*This prediction has been made regarding the fact that the potato pieces have all been taken from the same potato so as to keep the test a fair one.
Fair Test:
Fair testing is vital if the experiment is to work properly and produce accurate results. If this experiment isn't conducted fairly, the wrong results may be obtained, which could give the wrong conclusions.
All measurements and the weights of the solutions and the potatoes must be as exact, and as accurate as possible. The measurements of the potatoes will be as accurate as possible for every single potato, this will be done by evenly cutting the potato pieces, and making them all exactly 2.5g by wieghing them on electronic scales. This will enable us to make the wieghts more accurate than if using a manual balance. (Or than using length which is what we used in our preliminary experiment)
It will be nessecary to make sure that all the potato pieces are fully covered by the solution. This is because the potato should be fully submerged, therfore having total contact with the solution.
When using the balance, the balance must be reading zero before we put the potato chips on it. This is so that a false reading is not obtained.
And we will also be reading the measurements of the measuring cylinder by reading the bottom of the meniscus. We will use a burette to make our measuring for the solutions even more accurate than by eye (which is what we used in our preliminary experiment)
All the potato pieces in the different solutions will be left at room temperature for the same amount of time as each other to keep it fair.
Getting and experimenting with the exact measurements of molars and water is vital to this task. If the volume of one solution in a test tube is wrong then it will affect the pattern of results later on.
The potato should also be fully covered by the 6 different solutions. This is because, if the potato isn´t covered up by the solutions, the effect of osmosis might not occur to the fullest, and may in turn affect the results.
Method:
The variable in this experimant is the concentrarion of the solution. And therefore, everything else apart from this will be kept the same. First the pieces of potato will need to be cut and wieghed to the specific mass (2.5g). Once the potato has been peeled to remove the skin then small chips will be cut out using the cork boarer. Then the potato pieces will be cut, a bit at a time, and wieghed on the electronic balance. There will be 18 potato pieces in total that all wiegh the same, this is 3 pieces for each concentrations of the sucrose solution. I am using 3 for each so that an average can be taken from each concentration for more accurate results. The different solutions will be; Distilled Water, 0.2M sucrose solution, 0.4M sucrose solution, 0.6M sucrose solution, 0.8M sucrose solution and 1M sucrose solution.
Then the 6 sets of 3 potatoes will placed in the 6 test tubes at the same time.
As they must all be left for the same time then it is imperitive that when it comes to measuring there must be as little time difference between the weighing of the chips as possible, This is so that the results will remain as accurate as possible. We will dry them with the tissue paper, in sets of 3, and weigh and measure the potatoes taking in the average reading of the 3 pieces.
Ideally the experimaent could be repeated three times so that the three averages could form an overall average for even more accuracy but due to limited time this was not possible. Repeating the experiment multiple times would be a way of accounting for and hopefully eliminating any anomolous results.
Results:
Concentration of solution
Weight1st(g) potato
Weight2nd(g)potato
Weight3rd(g) potato
Average wieght of 3 (g)
Average increase/ decrease in wieght.
Pure Distilled Water
2.79
2.84
2.80
2.81
2.4%
0.2m sucrose solution
2.66
2.66
2.67
2.66
6.4%
0.4m sucrose solution
2.30
2.23
2.25
2.26
-9.6%
0.6m sucrose solution
.80
.98
.96
.91
-23.6%
0.8 m sucrose solution
.89
.87
.88
.88
-24.8%
molar sucrose solution
.86
.84
.83
.84
-26.4%
*1.80g*The red result in the table is classed as anomolous as it does not follow the pattern that all the others do. This means that the average result for 0.6m may be slightly anomolous too. In the table above shows the different concentrations of solutions, sets of 3 results for each, an average of 3 results and the average increase/ decrease in wieght as a percentage . The percentage increase/decrease of the weight of the potato is calculated by taking the weight increase/decrease divided by the original weight multiplied by a hundred. This should help lead to a more accurate result,and the average percentage will be used to present the graph.
Conclusion:
Enough data has been gained from this experiment to support the prediction. The investigation was successful and the results were similar to predictions.
Whilst working to stay alive the cells of the potato took in, or gave out the water depending on the concentration of the tissue, and the concentration of the solution surrounding it.
The results were as expected (apart from one which has been marked in a black circle on the graph and in red on the table in the results). The graph is linear which means there is a directly proportianal correspondance as predicted earlier. There was only one anomolous result which shows (disregaurding this anomolie) that the experiment was successful.
The results table and the graph as a result show that:
. In the experiment Osmosis was present in the potato cells.
2. As the molars of sucrose solution increased, the percentage of the weight difference decreased.
As the graph is directly proportional, matching to my hypothesis, then it is true to say the investigation must have been conducted well according to the method. It also shows that, from preliminary work and background information, there was sufficient information to make a well planned and accurate prediction.
To account for the anomolous result the experiment would needed to have been conducted several more times for more accurate and precise results, but a limiting time factor prevented the possibility of this. However it was not majorly disturbing to the outcome of the experiment as the line of best fit on the graph is still how was expected and the anomolous result on the graph has been high-lighted.
Evaluation:
The plan has been followed very carefully and precisley, and enough accurate and sufficient results have been obtained to conclude and evaluate the investigation, and to prove the prediction correct.
The final results were reliable, due to the care taken to make this a fair test. There was however one anomolous result. The first potato in the 0.6 molar sucrose solution category did not seem to follow the pattern of the rest. This could have been due to the fact that it may have come from a different potato to the others (great care was taken to make sure all chips came from the same potato), it may have been left in the solution for a different time to all the rest ( again great care was taken to make sure all chips were taken out at the same time and dried, wieghed and results recorded as quickly as possible), it may have been a mistake in the recording (either copied down incorrectly or a dodgy reading from the electronic balance). The anomolie could have been accounted for by a few repeats of the experiment so that more results for the same set of solutions could have been obtained creating a more accurate and reliable set of results.
To make this experiment better, I believe that we could have done more replicas for better results. Also I think that if there were a set of scales availlable exclusivley to our group then we would have been able to dry and measure the potato pieces a lot more quickly and accuratley than we did having to share with lots of other groups. This means that the time between taking the potato out of the solutions and getting them wieghed would be considerably shorter. We also could have got more people to do the experiment with us, so that we can organize the tasks, and we would be able to divide the tasks more efficiently.
If I were to do the experiment again but wanted to try and improve the outcome of the results then I would experiment with a wider range of sucrose solution (say ranging up to 2molar) and I would use smaller intervals ( say 0, 0.1, 0.2, 0.3, ... 1.8, 1.9, 2m) not only wolud this give me a more reliable and accurate set of results, it would also mean that when plotting a graph it would too be more accurate, and a lot easier to plot points creating a better graph.
In my experiment repeating the same tasks many other times would have been useful, since we had only done the results (set of 3) once, and NOT ALL the results were reliable, (there was the previously mentioned anomolie).
From this experiment there is large scope for future experiments that could use this investigation as preliminary work. For example simply changing a different variable, would lead on to a whole new experiment. This change could be either type of vegatable used (instead of potato a carrot may be used to see how the rate of osmosis differenciates between the two), age of vegatable (potatoes could be used that are different ages, such as 2months old, 4months, 6months, 8months, 10months and a year old to see how the rate of osmosis changes as the age of the potato increases) or the length of time that the potato is left in the same concentration of solution ( example: 10mins, 20mins, 30mins, 40mins, 50mins and an hour) *this was what we used for our preliminary work which we discovered the rate of osmosis becomes greater but directly proportionally until eventually an equilibriam is reached. Or the size/ surface area of the potato could be altered in the same concentration of sucrose solution. ( ie, lengths of 1cm, 1.5cm, 2cm, 2.5cm and 3cm, or wieghts of 1g, 1.5g, 2g, 2.5g and 3g to see how osmosis differs as the length/mass of potato increases.
![Determine the osmotic properties of a potato and how osmosis within the potato is affected in different concentrations of sucrose and water [molar solutions].](https://mbt-essays-prod-public.s3.eu-west-1.amazonaws.com/54655/listing/54655_1.jpg)
