AP Lab 1: Diffusion and Osmosis

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AP Lab 1 Diffusion and Osmosis

• Pre-lab Please take out your lab materials!

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Water Potential

• Water potential (y)can be thought of as being
  very similar to water concentration.
• Water will always move from an area of high water
  potential high water concentration to an area
  of low water potential low water concentration.

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Water Potential

• Water potential gradients can be thought of as
  being very similar to water concentration
  gradients.

membrane
Water concentration and potential gradient
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Add pressure

• Add pressure and you increase the rate of osmosis
  further!

membrane
Water concentration and potential gradient
Pressure gradient
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Solute Potential

• Solute potential can be thought of as being very
  similar to solute gradients. Solute potentials
  tend to be negative and run in the opposite
  direction of those of water.

membrane
Water concentration and potential gradients
Solute concentration and potential gradients
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The Equation and Beaker Problems

• The Equation
• Y water potential
• Y p pressure potential
• Y s solute potential

Y Y p Y s
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The Equation and Beaker Problems

• Add more water and Y increases
• Add more solute and Y s increases as well as Y
  decreases
• At atmospheric pressure, Y p 0

Y Y p Y s
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Beaker Problems

• Beaker Scenario

AFTER
Water Y 0
Water movement
Potato cell Y -3
Y p 3
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Change in Mass

• To calculate (formula p.5)
• change in mass Final mass Initial mass x100
  Initial Mass

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Calculation of Solute Potential

• Aside from getting Ys from the equation
  Y Ys Yp one can also calculate Ys
  from another equation!
• i 1
• C from graph 1.2
• R 0.0831 Lbars/moleK
• T in K (273 degrees C of solution)

Ys -iCRT
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Part 1A Diffusion Demo
BEFORE
AFTER
Water and IKI
Glucose and starch
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Part 1A Diffusion Demo
BEFORE
AFTER
Water and Benedicts
Glucose and starch
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Part 1E