Investigating The Affects Of Osmosis In A Potato

Neha Shah – 11EC

Investigating The Affects Of Osmosis In A Potato

AIM

To see how the concentration of sugar solution affects osmosis in a potato

PRILIMINARY RESEARCH

Osmosis is the process of movement (diffusion) of water particles from a high concentration to a low concentration through a selectively permeable membrane. The direction and rate of osmosis is dependant on the difference in water concentration on either side of the membrane. Water will move into an area of lower water concentration until both sides are roughly equal.

A diagram showing water molecules will diffuse from Solution B to A.

Plants need water to maintain turgidity. When the plant has enough water, the body of the cell pushes outwards which gives the cells their shape and makes them firm. The firm cells are said to be turgid. When a plant cell doesn’t have enough water, the contents within the cell shrink, making the cell floppy. This means it has lost turgidity.

There are various factors, which affect the process of osmosis.

Concentration of Solution – The concentration in which the potato cylinders are put in are affected by osmosis because there will be different concentrations of water and sugar in the solution and in the potato. A change in concentration can affect the diffusion of water.
Size of Potato – A large sized potato is likely to contain more substances. Therefore it is likely to contain more water, which can affect osmosis as there will be an increasing concentration of water, which, as the potato’s size increases affecting the overall movement of water depending on the concentration of solution that the potato is kept in.
Volume of Solution – The amount of solution affects osmosis. If there were a large amount there would be more water molecules therefore different concentrations of water.
Weight of potato – The change of weight of a potato has similar affect to the change in size of a potato. If the weight increases the water content is probably going to increase affecting osmosis.

PREDICTION

I predict that as the concentration of the sugar solution increases the rate of osmosis will also increase therefore the potato will shrink or decrease in length.

I also predict that when the potato is put into the distilled water the potato will expand or increase in length because there will be a higher concentration of water molecules in the distilled water than inside the potato cylinder. Therefore water will move in (from high concentration to low concentration). This will also increase the weight.

HYPOTHESIS

I believe this prediction because as the concentration of the sugar solution increases ...

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PREDICTION

I predict that as the concentration of the sugar solution increases the rate of osmosis will also increase therefore the potato will shrink or decrease in length.

HYPOTHESIS

I believe this prediction because as the concentration of the sugar solution increases the water concentration in the sugar solution will decrease. This means that the water in the potato will move out because there is higher concentration inside the potato than in the solution. This can be explained using the theory of water movement that water moves from high concentration to low concentration. Because the potato will shrink I think that the weight of the potato will decrease because water will move out therefore the mass will be lower also making the potato wilted.

FAIR TEST

To keep this whole experiment fair, I will make sure I record my results as accurate as possible. I will take out the potato cylinders at end of the 25 minutes. Also, I will cut the potato cylinders equally making sure they are all equal weight. I will repeat the experiment three times giving me a more variety of results.

However one factor that will change is the concentrations of the sugar solutions.

METHOD

Collect all the equipment – core borer, potato, white tile, stop clock, 5 beakers, measuring cylinder, distilled water and sugar solution of 4 different molars of 0.5m, 1m, 1.5m and 2m.
Using the core borer, cut out 15 pieces of potato all of equal mass at 0.40g.
Place 3 of the pieces into each of the concentrations and the distilled water.
Leave the potato cylinders in for 25 minutes.
Take them out the beakers and note the results down in a table shown. Then find the average.

RESULTS

The original mass of the potato cylinder before it was put into the solution was 0.4g.

The formula below shows how I calculated the average mass:

Average mass (g) = (a + b + c) / 3

GRAPH OF RESULTS

Here is a graph showing the average mass of each potato cylinder that was in the different sugar solutions and distilled water.

CONCLUSION

The evidence obtained from this investigation supports the prediction I made. In the graph it shows that as the concentration of sugar solution increases, the mass of the potato decreases because there was a lower water concentration in the potato.

The points on my graph line up with the line of best fit. However the two anomalous results that do not line up, still doesn’t prove my hypothesis wrong because they show a steady decrease in mass of the potato to the level of concentration of the sugar solution.

By looking at the mass before the experiment and after the potato cylinders have changed accordingly to its concentration that it was put into consistently.

EVALUATION

I believe we gained accurate and sufficient enough results, shown on our graph and tables that concludes the experiment, and to prove our hypothesis. My final results were very reliable, due to the precautions I took to make this a fair test.

Looking at the overall experiment I have thought of a number of improvements to give me more and better accurate results. Firstly the different sugar solutions could be made more accurate. Also when taking out the potato cylinder from the concentrations they could have been more properly dried to remove surface liquid which may affect the mass of the potato. It could give a more accurate result. Another thing I could have to improve my resulting was to measure the diameter change of the potato, which would have helped me to find out the volume before and after of the potatoes, which would also help me to explain the results obtained.

To make this experiment better, I believe that I could have done one test one at a time. While taking down the results for one set, the next set could be in the process of the experiment. This however would mean more time, but would make more accurate results. I also could have got more people to do the experiment with me, so that I can organise the tasks, and we would then be able to divide the tasks helping us to get more accurate results. Also using a different range of sugar solution concentrations; a more discrete set of concentrations for example 0.25m, 0.5m, 0.75m, 1m. This would produce more accurate results.

In terms of results I could change the shape and size. However this would not affect the results much. This is because the variable would only change the rate of osmosis because of a different mass and size.

To extend the investigation of osmosis, I could experiment on a leaf. In the same way I did with the potato cylinders I could use leaves instead. I would check the surface area as well as the mass of the leaf before and after the experiment.