Safety precautions: The main safety precaution I will have to consider is that I will be using a knife, which is dangerous and care must be taken. Also I must be careful not to get any of the sucrose solution in my eyes, as it will irritate.
Prediction: I predict that when the potato is placed in distilled water or very low concentration of sucrose solution, water will move into the potato and the cells in the potato will become turgor. When the potato is put in a higher concentration of sucrose solution the water in the cell will move out the cell and it will become plasmolysed. I predict that between 0.3 and 0.4M sucrose solution the cell with nether increase or decrease in mass and volume and won’t become either turgor or plasmolysed.
Scientific theory:
Osmosis: Osmosis is the movement substances through a semi-permeable membrane. The cell membrane allows some substances through and stops others. In general particles, which are bigger than the pores in the membrane are stopped, and particle, which are smaller, are let through. If two substances are separated by a semi-permeable membrane it water flows from the higher concentration side to the lower concentration side. Water will move until the concentration of water is equal on both sides, this is called osmosis. Osmosis gives rise to osmotic pressure and water pressure which effect osmosis. Water potential is the ability of water to move in this case through a semi-permeable membrane. Pure water has the highest water potential, 0, and has the greatest ability to move.
Water potential = psi
Cell = s + p
S = solute potential
P = pressure potential
Fair test: There are many factors that I have to consider to enable this experiment to go as fairly as possible. The factors that I need to keep the same are: obviously I would need to keep the size, shape; mass the same with the potato cubes or the test would not be fair. The distilled water would need to be the same as this could affect the results. The time of how long the cubes stay in the solutions has to be the same for all cubes otherwise it’s unfair. Also if I leave the potato chips out for a while they start to go brown which could affect the results.
The factors that I am able to change are: The concentration of sucrose and water. I can also change the temperature, as the temperature has no effect on the rate of osmosis.
Results:
Analysis and conclusion: My results show that when the potato was put in a solution which was high concentration of water the potato increased in mass, and when the potato was put it a solution of low concentration of water, the potato lost mass and became plasmolysed. This backs up my scientific theory well and show that my prediction was correct. There is a point where there is a concentration of sucrose solution which wouldn’t of made a difference to the mass and volume of the potato.
Evaluation: Overall my experiment went well and I got good reliable results but I could of improved them by measuring a few factors more accurately. I could of measured the surface area of the potatoes more accurately and I could of made the weight of the potatoes closer to each other or measured the weight of each and recorded it, then worked out the percentage change with it’s individual weight. Also while I was cutting and measuring some of the potatoes the others would start going brown which could of effected the results. After the potatoes were removed from the solution we had to dry them and some could have been dried more than others which could of effected the results.
