Investigate the effects of different concentrations
of salt solution on potato cells
Osmosis is the way in which many living things take up water (source:
GCSE Biology for You). During osmosis, water moves from a dilute
solution to a more concentrated solution through a semi-permeable
membrane. This membrane allows water molecules to pass through easily,
but does not allow solute molecules to do this. The movement of these
water molecules gradually dilutes the solution that had the higher
concentration until they are equal, or as close to equal as possible.
The following is a practical example that effectively demonstrates
% change in mass
Mass at start (g)
Mass at end (g)
From this example, we can see that example A reduced its weight by
4.9g, meaning that water molecules moved from the pure water into the
salt solution through osmosis. Similarly, example B gained 4.6g,
meaning that water molecules moved through the semi-permeable membrane
from the lower concentration of salt solution to the higher
concentration through osmosis.
à 3 galley pots
à 60 ml saturated salt solution
à 60 ml distilled water
à potato chips
à balance (accurate to 1d.p.)
à 50 ml measuring cylinder (accurate to 1ml)
à stopclock (accurate to 1d.p.)
à Size of potato chip
à Time left
à Surface area of potato chips
à Age of potatoes
à Concentrations of salt solution
à Temperature of potato chips/solution/surrounding area
Chosen variable: Concentrations of salt solution. I chose to use this
variable as it can be easily done and is easy to measure. It also will
give very clear results that are easy to analyse. I chose not to use
the mass of the potato chips or the age of the potatoes as this will
not produce very clear results to do with osmosis. I also decided not
to use the surface area or size of the potato chips, or the amount of
time left for these reasons. I believe that changing the
concentrations of the salt solution that the potato chips are in will
give me the most accurate and relevant results about how osmosis can
affect the mass of potato chips in salt solutions.
à Put 40ml distilled water in the first pot and label.
à Put 40ml saturated salt solution in the second pot and label.
à Put 20ml saturated salt solution and 20ml distilled water in the
third pot and label.
à Into each pot, put 3 potato cubes of a very similar total mass. Pat
dry with paper tissue before putting the cubes into the pots. Record
the total masses of the cubes.
à After adding the potato cubes simultaneously, start...