Imagine a narrow pipe, filled with fluid, in which the concentration of a certain type of molecule varies only along the length of the pipe (in the x direction). By considering the flux of these particles from both directions into a short segment [tex]\Delta[/tex]x, derive Fick's second law, dn/dt = D d2n/dx2 (those should be partial derivatives not normal ones) where n is the particle concentration and D is the diffusion coefficient.
Jx = -D dn/dx
where J is the particle flux
The Attempt at a Solution
I don't even know where to start