Investigate what happens to a potato chip's weight when placed in different concentrations of Sodium Chloride.

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AIM:~

To investigate what happens to a potato chip’s weight when placed in different concentrations of Sodium Chloride

INTRODUCTION:~

Osmosis is defined as ‘the movement of water molecules from an area of high water concentration to an area of low water concentration, across a semi-permeable membrane’ (Collins, 1999). A semi-permeable membrane is a membrane that partially allows liquid to pass through. In the case of the experiment I am carrying out, the potato chips have small holes in their membranes, which only lets some water molecules flow in and out of the solution and potato chips depending on the concentration of both.

In a high concentration of water the amount of solute (e.g. salt) is low.  This would be called a weak or dilute solution.

In a low concentration of water the amount of solute (e.g. salt) is high.  This would be called a strong or concentrated solution.

When two such solutions are divided by a semi-permeable membrane the water will move from the area of high concentration to the area of low concentration, until both sides are equal or have reached ‘equilibrium’.

                  Dilute Solution                          Concentrated Solution

Plant cells always have a strong cell wall that surrounds them. When osmosis takes place, and they soak up water, they start to swell. However the cell wall stops them from bursting as it is made from cellulose, which is very strong.

When plant cells are put into dilute solutions they become ‘turgid’, which means hard. Turgidity is important in plants, as it is this what makes plant stems strong and upright. Pressure inside the cell (when in dilute solutions) rises, and eventually this pressure is too high that no more water can enter the cell. The potato cells would increase in length, volume and weight because of the extra water.

When plant cells are put into concentrated solutions they lose water by osmosis and become ‘flaccid’, which means the opposite of turgid – limp. The contents of the potato cells shrink and pull away from the cell wall. These cells are said to be ‘plasmolysed’.

When plant cells are put into solutions that have the same osmotic strength as the plant cells, they are in a state between turgidity and flaccidity. This is called ‘isotonic’, meaning equal. The potato cells will have decreased in length, volume and weight.

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VARIABLES:~

To create a fair experiment, I am going to use 3 different variables:

        

        The Independent Variable

        The Dependant Variable

        The Fixed Variable

The independent variable is the factor that I am going to change. I will change the concentrations of solution. The different salt concentrations will be changed so that I can see the difference of the potato chips when placed in different molarities (strengths) of NaCl.

The dependant variable is the factor that I will measure. I will measure the weight change of the potato chips before and after being placed ...

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