Table of Contents

• Prequiz...
• Just Plain Movement
• 1: Measuring movement
• 2: Directed vs. undirected movement
• 3: Measuring movement using flux
• Introducing Gradients
• 4: Gradients and diffusion
• 5: Watching diffusion happen (applet)
• 6: Visualising the Gradient
• Fick's Laws, Part I
• 7: Fick's First Law
• 8: The gradient in Fick's First Law
• 9: A familiar equation for Fick's First Law
• 10: Graphing Fick's First Law
• 11: How does flux depend on distance?
• 12: A fragrant example
• 13: General transport equations and Fick's First Law
• Review
• 14: Summary

Summary

• Flux is the movement of particles per time (through a given area).
• In diffusion, individual particles are moving at random, and net movement is a result of more particles moving from high to low concentrations than are moving from low to high, thus, (Fick’s First Law)

 

• Fick’s First Law shares the same form as several other transport equations.
• D (the diffusion coefficient) has units of m² s^-1 or cm² s^-1, and is NOT equal to the speed at which an individual particle moves.

Learning Outcomes

You should now be able to:

• Explain the linear relationship between the rate of movement of a substance and its concentration gradient (Fick’s First Law).
• Measure the rate of movement of a substance from one area to another as a function of the concentration gradient and the diffusion coefficient for that substance in the medium.

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