Difference between Diffusion and Absorption

Diffusion is when a substance most likely a gas passes through a material without any pressure being applied. Diffuse a slow process spreading around. Nothings in a big hurry.

Now absorption is where a substance is taken up by another substance Sponge water. Blotting paper ink. The substance being absorbed is retained in the matrix of the absorbent material. Hydroscopic materials absorb water. Gasses can be absorbed as in oxygen into the blood. Drugs are absorbed.

Diffision is driven by concentration gradients. Absorption is driven by interactions like Van Der-Waals forces or electro-chemical potentials.

Gold and silver diffuse readily in tin. This is atomic diffusion where atoms pass through interstitial spacing or through substitution diffusion. There are a number of diffusion mechanisms and some are very fast. Diffusion is often modeled as 'random-walk across a concentration gradient'.

The differences between absorption and diffusion can be subtle, such as water vapor absorbing into silica sol-gel (arguably adsorption versus absorption that's a different issue). The questioner asked a good question.

También se aplica a una longitud de onda; en espectrometría, la transmitancia o difusión es la cantidad de luz que deja pasar un elemento a ser medido, y la absorbancia es la cantidad de luz que absorbe el mismo. - Esto puede variar según la longitud de onda usada. - Una aplicación directa es la espectrofotometria, y la identificación o concentración del elemento muestra. - (UV – VIS – IR), todos los elementos tienen una huella única, que por medio de esto se determina que es y en que concentración.

Good point, is it a materials question or a energy question.

Gracias por tus palabras, me refuerza las ganas de poner un granito del conocimiento adquirido en mi vida, pense que estaba fuera de sintonia.

Pregunta: Quien eres, GUEST, no puedo ver tu perfil.

Hablo, leo y escribo en ingles, pero creo que todos debemos de darnos un esfuerzo por entendernos en una misma idea - "las ganas de conocer mas", las mismas gracias a Vulcan que se toma la molestia de entender. -- QUE EL IDIOMA NO SEA UN IMPEDIMENTO --.

Mr. Grage Tesla was speaking of light absorption in a medium (such a solution of dye in water perhaps) versus light diffusion by scattering off particles.

Absorption of a chemical (along with possible chemical reaction ) may take place typically by a medium with a large surface area (although the technical interaction my also involve surface adsorption (not strictly absorption), but it usually due to the absorbed chemical entering into voids and being trapped there, since diffusion out of those voids is impeded by wall collisions.

good question