In my experiment, I am trying to find out how the concentration of a sucrose solution which pieces of potato are placed in affects how the mass of the potato changes due to osmosis.

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Biology coursework

How does the concentration of a solution affect change in mass caused by osmosis?

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Osmosis is the diffusion of water form a dilute to a concentrated solution of water. Cell membranes are partially permeable, which means water molecules fit through, but other, larger molecules such as glucose or sucrose (as in my experiment) cannot.

When cells are placed in an extremely dilute solution, water rushes into the cell, which causes the cell to become swollen. When they are placed in an extremely concentrated solution (more concentrated than the solution inside of the cell), water moves out of the cell, causing them to become shrivelled. Either of these extremes can be dangerous to the cell, causing them to be damaged and stop working properly, or even burst and die.

In my experiment, I am trying to find out how the concentration of a sucrose solution – which pieces of potato are placed in – affects how the mass of the potato changes due to osmosis.

I conducted a preliminary experiment first, to decide how to do my experiment. I measured 10mm lengths of a 5mm diameter potato core, and placed them in 10cm3 solutions of various concentrations. I used 0.5M sucrose solution diluted with water in the following proportions: 100% sucrose, 80%, 60%, 40%, 20%, and 100% water. These are the results I got from my preliminary experiment:

The measurement for 40% seems to be an outlier. I believe this is because measuring length is not very accurate. However, after discounting this result, there seems to be a slight pattern.

From my preliminary results, I decided to change and keep the same the following things:

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  • I decided to use larger pieces of potato in my real experiment, so any changes would be more obvious and so my measurements could be more accurate.
  • I also chose to measure the mass of potato pieces using a set of scales with 2 decimal places of accuracy. This made my measurements much more accurate.
  • I chose to repeat my experiment three times for each concentration, to make my results more reliable.
  • Because of this, I placed all three pieces of potato in the same beaker (this time with 100cm3 of solution). This could mean that if the concentration ...

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