Osmosis and
Water Potential
of a Potato
Emma Macadam
And
Marc Brunton
Hypothesis
 Our
hypothesis is that the potato will have
the highest water potential than the
butternut squash, sweet potato, and the
apple, assuming it has the lowest sucrose
concentration.
 We predict the apple will have the lowest
water potential, assuming it has the
highest sucrose concentration.
The Experiment
 Our
experiment tested the water potential
of a potato. There were six different
sucrose solutions, with varying molarities.
 By calculating the change in mass, we
predicted the molarities of the various
solutions. The larger the increase, the
lower the molarity, and vice versa.
 This is because water flows from low
concentration to high concentration.
Solution
Type
Blue
Solution
Orange
Solution
Yellow
Solution
Red
Solution
Green
Solution
Purple
Solution
Original
mass of
the
potato
(g)
5.3
4.7
4.8
4.8
4.4
5.4
New
mass of
the
potato
(g)
3.42
5.13
4.96
3.04
3.64
3.68
8%
increase
3%
increase
37%
decreas
e
17%
decreas
e
32%
decreas
e
Data Table
Percent
35%
change
decreas
in mass
e
of potato
Molarity of the Solutions
Orange- 0.0M
 Yellow- 0.2M
 Green- 0.4M
 Purple- 0.6M
 Blue- 0.8M
 Red- 1.0M
Orange had the highest increase, and therefore
the lowest molarity. Red had the highest amount
of decrease, and therefore the highest molarity.

Graph of the data
Color
Percent Change
0
0.08
Yellow
0.2
0.03
Green
0.4
-0.17
Purple
0.6
-0.32
Blue
0.8
-0.35
Red
1
-0.37
Percent Change in Mass of Potato
Percent Change
Orange
Molarity
0.15
0.1
0.05
0
-0.05 0
-0.1
-0.15
-0.2
-0.25
-0.3
-0.35
-0.4
0.2
0.4
0.6
Molarity
0.8
1
1.2
Estimated Molarity of the
potato
 We
estimate the molarity of the potato to
be around 0.3M. This is because at 0.4M
the mass decreased, but at 0.2M the mass
increased. The middle value is a good
estimate of what the molarity of the
potato might be.
Water potential of the potato
 Water
Potential= Pressure Potential +
Solute Potential
 Pressure Potential=0
 Solute Potential= -iCRT
 i-ionization constant, C=Molarity, Gas
Constant (0.08321), T= Tempurature
(Kelvin)
 -(1)(0.3)(0.08321)(273+21)= -7.34
Conclusion
 The
solution went from an area of low
concentration to an area of high
concentration, causing the potato to
shrink in a higher concentration solution,
and expand in a lower concentration
solution.
 The Potato had a relatively high water
potential, because it did not have to be in
a very high concentration of sucrose
before water started to leave it.
Xylem Tissue
 The
Xylem tissue’s main function is to
transport water and nutrients from the
roots, throughout the plant.
 Water moves upwards from the roots to
the leaves, because the water potential is
more positive in the leaves than the roots.
This allows water to flow from an area of
low concentration to an area of high
concentration.