Kay Bromley P3
Investigation into Osmosis
in Potato Cylinders.
Planning
I am investigating the effect of osmosis on a potato. Osmosis is the diffusion of water down a concentration gradient through a semi permeable membrane.
I am investigating the effect of water concentration on the potato cylinders. This means that I will put potato cylinders into salt solutions of different concentrations.
Factors
- Size of cylinder
- Volume of solution potato is in
- Time left in solution
- Surface area of potato cylinder
If I am going to make this a fair test, then I will have to control these other factors.
The size of the potato is very important. This is because if the size of the potato varies, so will the amount of mass it can loose or gain. I am going to try to cut all the pieces of potatoes, to the same size. To ensure this I will use a cork borer. I will have cylinders with the same width and height, but the length of the cylinders will differ. I am going to cut the cylinders to 3cm in length.
The light intensity cannot really me measured or kept the same, as the cylinders will be moved from one room to another, for storage. However I will try to keep the cylinders in the same place when I am storing them.
The mass of the potato is a variable, and this means that it will be measured throughout the experiment. I will measure the mass in grams. The potato cylinder will be measured before it is put in the solution, and after. This will allow us to see whether osmosis has taken place, and how much osmosis has occurred.
The volume of the solution that the potato cylinders are kept in must be the same. The cylinder must be totally covered in the solution, and the amount of solution will be kept the same because all the cylinders are the same size. The amount of solution I cover each cylinder in will be 25ml.
The type of potatoes I will use is going to be kept the same, because different potatoes may absorb at different rates. For this experiment I am going to use the same potato.
The time the potato cylinder is left in the solution must be kept the same for each cylinder. This is because more or less solution may be absorbed depending on time. I am going to keep each potato cylinder in each solution for nine days.
The surface area of the potato cylinders will be kept the same by having all the cylinders the same size. This must be kept the same because the amount of surface area exposed to the solution may effect the rate of osmosis. The thickness of the cylinder will already be the same, so I will cut the length of each cylinder to 3cm long.
To make the mass readings more fair, I will take each cylinder, roll the cylinder gently on a paper towel, to remove all excess solution, and I must not squeeze the cylinder.
I am also going to use the same balance to weigh my cylinders. This is because the measurements may vary slightly between scales.
