MOLECULAR TRANSPORT OF MATTER

Diffusion is the transport of matter caused by a concentration gradient. Matter is transported from areas of high concentration towards those of low concentration, i.e. in the opposite direction to the concentration gradient. The corresponding law is FICK s law. Two other phenomena of molecular transport of matter exist one results from a temperature gradient, this is the SORET effect the other is due to a pressure gradient and is called barodiffusion. These two diffusion fluxes are negligible with respect to pick s diffusion in most cases. 

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