Investigate the factors affecting the rate of Osmosis

Investigate the factors affecting the rate of Osmosis

Planning

Osmosis is the diffusion of water from a lower concentration of solute to a higher concentration of solute, through a partially permeable membrane. In a high concentration of water the amount of solute (e.g. sucrose) is low. This could be called a weak or dilute solution. In a low concentration of water the amount of solute is high. This could be called a strong or concentrated solution. When a partially permeable membrane divides two such solutions, the water will move from the area of high concentration to the area of low concentration until both sides are equal. In plant cells water flows through the cell wall and cell surface membrane into the vacuole from the outside. As a result, the cell swells up. It doesn't burst as the cell wall stops the cell expanding too much; at this point we say a cell is fully turgid.

Aim

The purpose of my investigation is to investigate the factors affecting the rate of Osmosis. The key factors I have found affect this are:

Length - of membrane

Temperature - of water

Concentration - of solution

The factor I am going to investigate is the concentration of the solution in which the potatoes are placed. By doing this I will have to control all other factors to ensure a fair test, these are; doing all the tests at room temperature to control the temperature as a higher temperature would mean diffusion would occur quicker. The mass and surface area of the potatoes at the beginning of the experiment are other controls I will need to monitor to ensure a fair test. The mass of the potato is a dependent variable; this means that it will be measured throughout the experiment. I will measure the mass in grams correct to 2d.p. The potato chip will be measured before it is put in the solution, and after. This will allow us to see whether osmosis has taken place, and to what extent.

The volume of the solution that the potato chips are kept in must be fair. The must be totally covered in the solution, and the amount of solution will be kept the same because all the potato chips are the same size. The amount of solution I cover each chip in will be 20cm.

Prediction

I predict in my experiment that the higher the concentration of sugar in the solution, the smaller the potato chip will become. I predict this as the greater the concentration of water in the external solution, the greater the amount of water that enters the cell by