13: 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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