Water Potential Potential energy of water per unit area compared to pure water.
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Transcript of Water Potential Potential energy of water per unit area compared to pure water.
Water PotentialPotential energy of water per unit area compared to pure
water
Water Potential =
• Allows us to determine where water is going to flow due to osmosis, gravity, pressure surface tension
• Into or out of cell?so cruel!
Out
side
of ce
llIn
side
of ce
ll
• Na+ and Cl- ionize and are surrounded by hydration shells
• Opens up all these excess spaces
• Decreases water potential
Out
side
of ce
llIn
side
of ce
ll• Water leaves
the cells of the slug
• Pure water = 0
• Water moves from greater water potential to less
Wat
er p
oten
tial
gr
adie
nt
Distilled H2O = 0 bars
Roots = -2 bars
Stems = -6 bars
Leaves = -15 bars
Atmosphere = -1000 bars
• More solute drops potential– Because it opens up spaces for
water to flow in• Physical pressure– Plant’s cell walls put pressure
back on water (+ because it is pushing water out)
-5 bars
2 bars = -3 bars
ψs = -iCRT • i = ionization constant (for sucrose, this is 1
because sucrose does NOT ionize in water• C = molar sucrose concentration at
equilibrium (determined from your graph…the point at which your line (of best fit) crosses the x-axis.• R = pressure constant (0.0831 liter
bar/mole °K)• T = temperature in Kelvins (273 + °C)
The molar concentration of a sugar solution in an OPEN beaker has
been determined to b 0.2 M. Calculate the solute potential at
22C.• i = 1 (sugar does not ionize)• C = 0.2 moles/liter (M)• R = 0.0831 liter bar/mole K• T = 22+ 273 KWhat is the OVERALL water
potential?Pressure potential = 0 in open container…
0.0
M
0.2
M
0.4
M
0.6
M
0.8
M
1.0
M
% c
hang
e in
m
ass
0
% change in mass of simulated animal cells containing various sucrose
molarities.
Molarity =
moles/liter
16
% CHANGE IN MASS OF POTATOES (1st period)Solution Solutio
n Color% ∆ in Mass
Molarity
Type of Solutio
n
Temp(K)
A Purple -13% 0.6 Hypertonic 294
B Green +24%
0.0 VERYHypotoni
c294
C Red -23% 1.0 VERYHyperto
nic294
D Yellow +4% 0.2 Hypotonic 294
E Pink -8% 0.4 Hypertonic 294
F Blue -13% 0.8 Hypertonic 294
% CHANGE IN MASS OF POTATOES (4th period)Solution Solutio
n Color% ∆ in Mass
Molarity
Type of Solutio
n
Temp(K)
A Purple -18% 0.6 Hypertonic 294
B Green +16%
0.0 VERYHypotoni
c294
C Red -33% 1.0 VERYHyperto
nic294
D Yellow +6% 0.2 Hypotonic 294
E Pink -14% 0.4 Hypertonic 294
F Blue -24% 0.8 Hypertonic 294
0.0
M
0.2
M
0.4
M
0.6
M
0.8
M
1.0
M
% c
hang
e in
m
ass
0
Molarity =
moles/liter
% change in mass of potato cells submerged in solutions of different
sucrose molarities.
10
20
-10
-20
0.0
M
0.2
M
0.4
M
0.6
M
0.8
M
1.0
M
% c
hang
e in
m
ass
0
Molarity =
moles/liter
% change in mass of potato cells submerged in solutions of different
sucrose molarities.
10
20
-10
-20
Sucrose molarity inside potato cells?Isotonic solution!C for equation!