Investigating isotonic point of a potato

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Bio Lab- 2                Amandip Toor

                IBD 1st Year

Investigating the Isotonic Point of a Potato

Aim: Finding the isotonic point of potato cells by testing it in different concentrations of salt water. 

This diagram shows the movement of water through hypotonic, hypertonic and isotonic. But what are the arrangements of molecule for them? This is shown on this simple diagram.

Hypothesis: I believe the isotonic point will be around 0.25 mol. This is because I feel that the 0.1 solution will be too hypotonic. Therefore I believe at around 0.25 there will be little or no change in the mass of the potato because I’m predicting that this will be the isotonic point.

Fair Test:

  • Three potato slices were used for each solution so that more accurate results could have been obtained.
  • All potatoes slices were of the same mass, this was done by using the same cork borer therefore the diameter was always constant so the volume would remain the same
  • All potato slices were taken from one potato so the cells will be similar.
  • The temperature will remain the same for all beakers.

Safe Test:

  • We will be using scalpel and cork borer therefore we made sure we handled them with care
  • We made sure we used the beakers appropriately, so that they did not brake and cause any damage.  
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Variables: Independent- Concentration of the solution

              Dependent   - Change of the mass of the potato chip


     -    Mass and volume of the potato chip

  • The size of the potato slice
  • Volume of the salt solution
  • Length of potato


  1. A raw potato
  2. Cork borers
  3. Scalpel
  4. Weighing scale
  5. Salt solution of concentration 0.1M, 0.2M, 0.3M, 0.4M and 0.5M.
  6. Tissue paper
  7. Cello Tape
  8. 5 Beakers


  1. Collect a fresh raw potato and remove the skin of it.
  2. Using the cork borers and cut ...

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