ask this question:
Does gravity affect molecules? The answer is yes; just think of Earth's atmosphere.
Then argue:
If yes, then why do molecules diffuse in solution, seemingly disobeying gravity?
You can demonstrate this with food dye and test to see if gravity or higher g's influence diffusion rates.
add dye to the bottom of a few beakers. Spin one at high speed, one lower, and leave one be. See which diffuses faster. draw up a few experiments all to test whether molecules in different mediums feel gravitational forces.