What do the units of diffusion coefficient mean?

[kop442000]

I see that the diffusion coefficient (of diffusivity) D has units of something like cm^2 / s. I'm having trouble understanding what those units mean.

For example, speed has such units because something travels a certain LENGTH in a certain TIME.

Could someone explain this for me?

Thank you.

 

[tiny-tim]

hi kop442000!

flux is speed times density,

so Fick's law is essentially:

flux = speed times density = diffusion coefficient times the gradient of density

so the diffusion coefficient is speed per gradient ie L/T per 1/L ie L²/T

so if you double the coefficient, you will either double the speed, or you will get the same speed for only half the gradient of density​

sorry, but it doesn't come any more intuitive than that