An investigation into osmosis using a pealed potato and different concentrations of salt solution.

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Sheena Shah

11AL

Osmosis in a Potato Chip

Aim:          

An investigation into osmosis using a pealed potato and different concentrations of salt solution.

Hypothesis: 

I predict that in this experiment, a higher concentration of salt solution will move to an area of low concentration of a solution.  The definition of osmosis that the CGP Science Book gives is “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.”  

This means that if the potato is surrounded by a solution, which has a low concentration, the mass of the potato will decrease, as the high concentration from the potato will move onto the water, there for increasing the volume of water surrounding the potato.  The partially permeable membrane in this experiment is the surfaces of the pealed potato.  It will let the salt solution pass in and out of it, therefore increases or decreasing the mass of the potato.

The GCSE Science Class book says, “Osmosis is a special type of diffusion.  It occurs across a permeable membrane, which allows some particles to diffuse through it and not others.  Most cell membranes are like that, being permeable to water and some solutes only.”  This means that the potato will definitely allow water to go in and out and should also allow the salt solution to enter it.

I predict that the higher the concentration of the salt solution, the more solution will move out of the potato chip.  Osmosis is the flow of a solvent of a solution, through a membrane.  The membrane blocks off the other components so that they cannot flow through.    

I will be using different molars of salt solution, so the mass of the potato will also be varied.  I predict that at a lower solution, 1.0 molar, the concentration of salt solution will move into the potato, as it will have lower concentration than the solution around it.  Therefore at a higher concentration, the potato chip will decrease in size, as it will have a higher concentration than the salt solution surrounding it.  

I believe that the molecules will continue to diffuse until the area where the molecules are reaches its isotonic point, which means that the molecules are randomly distributed around the potato.  No area will have a higher or lower concentration as they will both be equal.    

The diagram below shows how osmosis will occur.

Extra information on potato plant cells

Osmosis is found in animal and plant cells and occurs in a partially permeable membrane, which has very small holes in it.  The holes are so small that only water molecules can pass through and larger molecules cannot get through.  

Plant cells always have a strong cell wall surrounding them.  When water is taken into them by osmosis, they start to swell, however, to prevent them from bursting, the cell wall protects it.  The plant cells become turgid when they are put in solutions.  Turgid means being firm and swollen.  Inside the cell the pressure rises and eventually gets so high that no more water can enter the cell.  This information has been found from the Internet site    

Preliminary work: 

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In order to carry out a correct investigation and get accurate results, I will carry out a preliminary experiment first.  This should also help me back up my prediction and plan the investigation properly.  In this experiment, I will use a salt solution of 1.0 molar and pure water.  I will use 75.0cm³ of each substance as I feel this will cover the potato chip fully.  The length of the potato chip will be 3.0cm and I will put two of these in each solution, because this will give me an average result, which will be more accurate than one result.  I ...

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