An investigation into the factors affecting osmosis

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Planning

My aim for this experiment is to see the results of potato tissue's mass difference, when placed in different concentrations of sugar solutions.

Variables involved:

For this experiment I would expect to have 3 different variables, Independent, Dependent, and fixed variables, which all helps me to plan and explain the experiment thoroughly.

The Independent variable (things you change), the thing that I will be changing in this investigation into the factors affecting osmosis, is the concentrations of the solution that helps me to investigate osmosis with potato tissues. The different sugar concentrations will be changed to see the result of the potatoes when placed in sugar solutions placed in different molarities (strengths).

Dependent Variable (things that you measure) the things that I'll be measuring in this experiment on osmosis is the mass change and length change of the potatoes placed in different molarities of sugar solutions. I will record the masses in grams by using a balance and the length changes by using a ruler.

Fixed Variables (Things that you keep the same) the things that I have chosen to keep the same in each individual experiment to keep it a fair test is to keep the same sizes of each potato tissue the same by using the same cork borer and same ruler. I will be keeping the same amount of solution placed in the test tubes for each different experiment, which I will measure using a measuring cylinder. I will also be keeping the same potato through out the whole experiment to as using a different one might give me anomalous results as some might have more water in it then others.

Preliminary work:

For our preliminary work we looked at how the different molarities of solution affected the amount of osmosis in onions, and we found out that 0 and 0.1 molar solutions had increased greatly in size and mass. Whereas 1.0 and 2.0 molar solutions decreased the onion in size and mass. We found out that the ones that we couldn’t really see any particular difference in we would have too look in specific detail so we decided to look between 0.2M and 0.4M.

I will plot my results in a table that looks like this:

Hypothesis:

Osmosis is the passage of water molecules from a weaker solution into a stronger solution, through a partially permeable membrane. In this case, the tiny holes in the membrane of the potatoes will allow the water molecules to pass through in and out of the solution and the potato, depending on the concentration gradient of the two substances. So in this case, when the water concentration is lower in the tissue, the water will go inside the tissue of the potato, and the potato will gain mass. If there is very little different in the two water concentrations, there shouldn't be such a big change in mass. Also if there is a higher concentration of water in the potato, then the water will go out of the potato and into the liquid solution, as osmosis is the movement of water molecules from a region of high concentration to a region of low concentration, through a partially permeable membrane.

The potato, cut up into pieces, will need some sort of element to survive, and in this experiment, it would be light and water. With both of these sources, the potato will keep on working until it dies of either lack of water or too much water, or will stop, as both sides would become equal, making no more reactions. When the concentration gradient is lower in the potato, the water will transfer from the solution into the potato.

In the distilled water, I believe that the water is more concentrated in the potato, and therefore the water should transfer from the water to the potato, making the potato bigger in size, and heavier in weight. The potato tissues, being surrounded by a weak solution, will be most likely to swell up and become turgid, taking in all the water it can possibly take in. So I have chosen to leave it out due to our preliminary work, which showed that it would change a lot.

With the potato in 0.2 molar solutions of sucrose, I don't think there will be much change in the weight of the potato. This is because there isn't much difference between the two substances. I believe that the weight and the size of the potato won't be altered much.

The 0.24 molar solutions of sucrose, similar to the 0.2 molar solution of sucrose, compared to the potato, both substances have very close concentration gradients. And that is why I am predicting that the weight of the potato in this experiment should be decreased by only a fraction.

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The 0.28 molar solution of sucrose, I think, should make a slight difference now, noting that it should be a small difference between the two concentration gradients. And therefore the weight should decrease, not very noticeable for us but none the less there.

The difference between the water concentration in the potato and the 0.32 molar solution of sucrose will be relatively big, and the water in the potato should be transferred from the potato, through the permeable membrane, to the solution surrounding the potato. As a result, I am sure that the weight of the potato will increase by ...

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This is a well written and detailed report. 1. The variables sections cover the necessary information and set out the investigation well. 2. The report is missing an introduction section with relevant information. This information is scattered in other sections of the report. 3. The scientific information section contains relevant information that should be referenced. 4. The table of results is well presented. 5. The analysis summarizes the data but does back this up using the data itself. 6. The evaluation shows a good knowledge of scientific processes. ****(4 stars)