Osmosis in Potato Cells
Plan
Introduction
Given that osmosis is the movement of water molecules by diffusion
from a place where the water molecules are in a higher concentration
(high water potential) to a place where the water molecules are in a
lower concentration (low water potential) through a partially
permeable membrane, the experiment to test osmosis in potato cells was
set up. The experiment would prove the theory of osmosis and determine
whether the concentration of water in the solution surrounding the
potato was higher or lower than that of the water concentration inside
the potato. This would cause the potato to become turgid or
plasmolysed.
Diagram of apparatus
Variables and Method
Above all other factors, for this experiment to work it needed to be a
fair test. For this to be possible, all variables had to be controlled
throughout.
Seven separate concentrations of water and sucrose solutions were used
in this experiment with a maximum of 20% sucrose. These were
distributed accurately with the use of measuring cylinders as the
concentrations of water and sucrose held great sway on the dependant
variables, such as the mass or length of the potato at the end. Each
solution had a volume of 20cm and both the temperature and pH were
recorded.
It was necessary that all seven samples of potato had to be the same
length, width and therefore surface area before the experiment began.
This was so equal amounts of solution could make contact with each
potato and that there was the same amount of water inside each potato
to begin with. For accuracy a cylinder shaped cork borer of size five
was used and once all the samples had been pulled out of the potato a
metal rule marked 5cm of length on the potato and the left over were
cut off with a sharp blade. The mass of each potato was then recorded
to two decimal places using the balance so these could be compared
with the end results.