Osmosis

Sc1 Investigation - Osmosis

Planning

Input variables of this investigation I could study are the concentration of sugar in the solution, amount of water in solution, size of potato, the temperature of the solution, type of potato and the mass of the potato.

The variable I have chosen to investigate is the amount of sugar in the solution and how this will affect the results.

What I think will happen is that the higher the sugar concentration the bigger the gain in the mass of the potato. I therefore, predict that the lower the concentration of sugar in the solution the more the potato will lose mass. So if there is a gain in mass there will have been a high sugar concentration in the solution.

I think this will happen because of a ..... called osmosis. Osmosis is defined as the movement of water particles from a high concentration of water to, a lower water concentration through a selectively permeable membrane or semi-permeable. Pure water has the largest amount of free water molecules. When sugar dissolves into water the sugar molecules combine with water molecules. This in turn effects the concentration of free water molecules in the solution, due to the water combining with the sugar molecules there will not as many free water molecules to move via osmosis. Therefore this means the more sugar molecules in a solution the higher the concentration, this means the more concentrated a solution is the fewer free water molecules. This shows that if the potato were placed into high concentration solution the free water molecules would move from the solution to the potato cell. So when a cell is placed in distilled water (high water concentration) water will move into the cell (lower water concentration) using osmosis making the cell swell. This cell is now referred to as turgid. However if a potato cell is placed in a low water concentration, the free water molecules in the potato cell will move out into the water thus meaning the potato will lose mass. If the potato losses to much water then the cell membrane will break away from the cell wall and the cell will then be referred to as plasmolysed. Osmosis will continue to happen until the concentrations in the cell and in the solutions are equal or in equilibrium. the potato chip used for 0 molar concentration will gain water, as the water moves from a region

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