An investigation to determine the effect different concentrations on osmosis in a Potato.

9/6/03 GCSE Investigation Sc1 Josh Day

An Investigation to determine the effect different concentrations on osmosis in a Potato

For the experiment I will need to get the right shape of the potato and use the same size of that shape to keep the surface area the same and also keep that the same in each of the experiments to keep it a fair test. So I will get a cork borer and make cylindrical shaped potato pieces. Then I cut off the ends of the potato. I will also measure the length of the potato to 3cm

I am going to cut the size of the potato first and then I will put the solution in until it covers the potato. I will measure out just enough solution just to cover the potato chip and this should be about 20 ml. I will cut eight potato chips for the experiment and use the same amount of solution. This will be a factor which will stay the same as well the size of boiling tube and length and width of potato chip.

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I will do three different times for the different solutions. The first time will be for 20 minutes, the next 40 minutes and the last for 17 hours. This will give a chance for me to see if tit is time which contributes to the amount of water transfer. I predict that time will have a major effect on the amount of the water transfer which occurs. I predict that the longer the experiment goes on for, the greater water transfer will occur to a certain extent. But eventually the solution will reach equilibrium. This means that the solution outside the potato chip has the same water potential as inside the chip. The water will just keep flowing equally between the both and not much mass change will take place. Something like 30 hours would just not be sensible because there would not be much difference between 15 and 30 hours.

Temperature will also need to be just right. I think that as the potato is made up of living cells, the potato chip will function properly at its optimum temperature. If the temperature is too much the partially permeable membrane will be ruptured therefore much more water will diffuse through it. So I think if I use 37C, which is body temperature, then it will be the right temperature to use. But I will also try room temperature just to check. We are not going to change the potato because the partially permeable membrane will be different on each potato. The potato might be old and have a hard skin and therefore water will not diffuse as well, as in a new potato.

The last point I will investigate is the concentration of the solution. I will only investigate two different concentrations. One will be pure water and one will be 10% sugar solution.

I think that the potato chip will not absorb as much of the 10% sugar solution than the pure water. This is because there are more water particles in pure water than in 10% sugar solution and therefore the potato will be able to absorb more water from the pure water solution.

Results of the Preliminary Work

Apparatus