practical was aimed at investigating how the mass of potato chips changed
depending on the concentration of solute in the solution over a period of time.
This change in mass occurs due to osmosis. Osmosis is the process of water
molecules moving from an area of high water potential to an area of low water
potential. When a solute is added to the water, the solution has a low water
potential. This results in water molecules moving from the area where there are
fewer solute molecules (high water potential) to the area where there are more
solute molecules (lower water potential) through a semi-permeable membrane.
plays an essential role in cells and therefore it is crucial that osmosis is
understood through such experiments such as this one. Osmosis is required to
ensure that the internal environment of an organism is stable. This is achieved
by ensuring that concentration of solutes and water potential are balanced. When
there is a greater concentration in the solution than inside the cell, then the
solution is hypertonic and water is passed to the exterior of the cell. If too
much water is drawn from the animal cell, the cell can shrivel. In plant cells,
as the cell wall is stronger than that of animal cells, instead of shrivelling
up, cells tend to become limp. If a solution is less concentrated than the
interior of a cell then the solution is hypotonic. This results in the cell
absorbing water from its exterior. If there is an excessive amount of water
being absorbed into an animal cell, it can lead to the cells bursting. In plant
cells, the cell wall is rigid, so instead of bursting, the cells become turgid.
When a solution has an equal concentration as the inside of the cell the
solution is known as being isotonic. This results in an equilibrium between the
exterior and interior of the cell.
hypothesis for this practical was that, by increasing the solute concentration,
the mass of the potato chips will be lower. The overall goal for this
investigation was to prove the theory of the hypothesis that a change in the
solute concentration will have an overall effect on the mass of the potatoes by
either causing an increase or a decrease.
In order to study the effect of
solute concentration on osmosis, there were two parts involved in the method.
Part one used ready cut chips which
would have been soaking in water for one hour. Six test tubes were labelled
with the concentrations of NaCl. These test tubes were labelled 0%, 20%, 40%,
60%, 80% and 100%. Potatoes were collected, peeled, cut into equal chip sizes
and dried on a paper towel. The potato chips were individually weighed and
noted down. After ensuring all chips were dry, individual chips were
subsequently added to the test tubes. Once each test tube had a potato chip, ensuring
which potato went in which test tube is critical for the results. Test tubes
were then left for a period of twenty minutes. After the time was complete, the
potato chips were carefully removed from their test tubes and dried on a paper
towel. When the potato chips were dry, they were reweighed and the results were
were recorded into two tables (Table 2, Table 3) and subsequently a graph was
formed (Figure 1). Results showed that there was a positive percentage mass
change where the concentration of NaCl was 0% (Table 2). For the remaining
results, the percentage mass change was negative. (Table 2, Table 3).
The graph shows
a deep decline on both the pre-soaked chips and the freshly cut chips. (Figure
1) The line showing the results for the pre-soaked chips falls to -22.278% before
it inclines slightly reaching -18.773%. Here the line steeply falls to the
lowest mass change of -30.236%. (Figure 1)