Investigating the Factors Which Affect Osmosis
The aim for this Biology coursework is to investigate hoe the
concentration of sodium chloride will affect the mass of potato chips
that will be the same length and have same width. The time factor for
the chips will be the same to make it a fair test. The main variables
throughout the investigation will be the mass, the length and the
concentration in which the chips are kept in.
Scientific knowledge of osmosis
Osmosis is the movement of water particles across a semi permeable
membrane, from a dilute solution to a more concentrated solution,
until equilibrium is established, i.e. the same number of water
particles on either side of the membrane.
As the potato cell contains a more dilute solution. Water will pass
into the solution to try and balance both things out. If the salt
solution inside the vacuoles of the potato cell is less dilute than
the solution in which it is planted in, water will enter the cell
vacuoles in which the chips will gain mass and length.
How ever, as the osmotic pressure builds up inside the vacuoles less
water molecules will pass into it. Again when the osmotic pressure
inside the vacuoles is the same as the water pressure outside there
will be the same number of water molecules entering and leaving the
cell. In this case equilibrium is relived.
When placed in the solution water will pass out of the cell as the
more concentrated solution is outside the cell. The longer the chips
stay in the solution the more mass will be lost as much more osmosis
occurs. When the cell has lost as much as water as it can it is said
to be plasmolysed (membrane has shrunk into the middle of the cell,
and therefore no osmosis can occur).
When the cell wall has become very firm and strong, the cell has
become turgid. This prevents the cell wall from bursting open as the
cell swells because of the amount of water entering the cell.
But the opposite of this is when the cell becomes flaccid. That is to
say when the cell has become limp and weak, no longer firm. This is
when the cell is losing rapid amounts of water, eventually becomes
If a plant cell is surrounded by a solution more concentrated than the
cell sap, water passes out of the vacuole to the out side solution.
Loss of water causes the vacuole to shrink and pull the cytoplasmic
lining away from the cell wall and the cell is flaccid. This
condition, called plasmolysis, can induced experimentally in living
cells with out necessarily harming them, but it is an extreme
condition but it rarely occurs un nature. But for humans, the cell is
very different to plant cells. As humans cells don’t have a cell
wall, so our cells can’t become turgid, as a result are cells could
burst open, because of the amount of water filling up in...