See the results of a potato tissue's mass difference, when placed in different concentrations of sugar solutions.

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Investigating Osmosis

Aim

My aim for this experiment is to see the results of a potato tissue’s mass difference, when placed in different concentrations of sugar solutions.

Osmosis Explained

Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration. It can be affected by several different variables including concentration of sugars. In this investigation I will be exploring the effect of varying concentration of sucrose sugar solution on the amount of osmotic activity between the solution and the potato chip of a given size.

Osmosis is basically a special kind of diffusion involving water molecules, which occurs when two solutions are separated by a partially permeable membrane. The water diffuses from the weaker solution to the stronger solution. Tiny holes in the membrane allow small water molecules to pass through, but the glucose molecules are too large to pass through the semi- permeable membrane.

Plant cells have a cell wall surrounding them, this is very strong. When they take in water by osmosis they begin to swell, but the cell wall stops them bursting. Plant cells become swollen and hard when they are put in dilute solutions. The pressure inside the cell will rise and eventually is so high no more water can enter the cell. This works against osmosis. But being like this is very important to plants, as it is what makes the green parts of them stand up in the sunlight. When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become weak and thin, because the sugar is more concentrated outside the plant than in the plant itself. The insides of the potato cells shrink and pull away from the cell wall. When plant cells are placed in a solution, which has exactly the same osmotic strength as the cells they are in a state between swollen and hard and weak and thin.

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Variables

  • Temperature
  • Volume of sugar solution
  • Concentration
  • Weight of potato
  • Surface area

I have chosen to change the concentration because I hope this will give me a good varied set of results to work with. The concentration will be measured in molars.

To make sure this is a fair test I will have to keep all the variables constant apart from the concentration. If I did change one of these variables, for example, if one potato chip were 1cm longer than the other there would be more space for osmoses to ...

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