there are many, many, many places in nursing where osmosis and diffusion are applicable.
dialysis is certainly one, albeit a complicated one.
there are others that are probably going to be easier. i'm going to give you some examples to get you started:
third spacing of fluid (esp in people with low albumin levels)
blood transfuisons: use ns only (never d5)
hypertonic vs isotonic vs hypotonic solutions.
tpn can only go through a central line
ok, as i type this, i'm looking at your background and i realize that as a prenursing student, some of this probably doesn't make much sense, right?
so to help some more (i hope), try focusing on the blood stream -- a mix of plasma, electrolytes, blood cells. what happens to the blood cells (and the cells lining the blood vessels) if you pour a concentrated (hypertonic) solution in via an iv? what happens if you infuse a very dilute solution (hypotonic)? if i tell you that tpn is very hypertonic, does that tell you anything?
hmmm, i'm probably causing more confusion than i'm helping -- sorry about that. it is tough for me to figure out how much to help since i'm not sure what your backgound/base knowlege is. i just really don't want to do the assignment for you, but i'll help as much as you need.
let me know if this helps, or how much i need to explain the above, if you'd like.