diffusion
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- Chemistry LibreTexts - Diffusion
- Denison Digital Commons - Diffusion and Random Walks (PDF)
- Indiana University Pressbooks - Basic Human Physiology - Diffusion
- RSC Publishing - Diffusion and flow in complex liquids†
- City University of Hong Kong - Diffusion
- Scholars at Harvard - Diffusion (PDF)
- California Institute of Technology - The Feynman Lectures on Physics - Diffusion
- IBM - What are Diffusion Models?
- OpenStax - Chemistry 2e - Effusion and Diffusion of Gases
- University of Cambridge - Department of Materials Science and Metallurgy - Introduction to Diffusion
- Science Education Resource Center - Teaching Mineralogy - Diffusion and Partitioning
diffusion, process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration. A familiar example is the perfume of a flower that quickly permeates the still air of a room.
Heat conduction in fluids involves thermal energy transported, or diffused, from higher to lower temperature. Operation of a nuclear reactor involves the diffusion of neutrons through a medium that causes frequent scattering but only rare absorption of neutrons.
- On the Web:
- Indiana University Pressbooks - Basic Human Physiology - Diffusion (May 08, 2026)
The rate of flow of the diffusing substance is found to be proportional to the concentration gradient. If j is the amount of substance passing through a reference surface of unit area per unit time, if the coordinate x is perpendicular to this reference area, if c is the concentration of the substance, and if the constant of proportionality is D, then j = −D(dc/dx); dc/dx is the rate of change of concentration in the direction x, and the minus sign indicates the flow is from higher to lower concentration. D is called the diffusivity and governs the rate of diffusion.
