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Encyclopedia > Physisorption

Physisorption is a process whereby a molecule adheres to a surface without the formation of a chemical bond, usually by van der Waals forces or electrostatic attraction. The formation of a chemical bond leads to chemisorption. The title given to this article is incorrect due to technical limitations. ... In chemistry, a chemical bond is the force, which holds together atoms in molecules or crystals. ... Chemisorption is a process whereby a molecule adheres to a surface through the formation of a chemical bond, as opposed to physisorption where that is not the case. ...


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Gas adsorption - porosity measurements (2059 words)
Thus physisorption experiments for surface characterization are performed at very low temperature, usually at liquid nitrogen or liquid argon boiling temperature at atmospheric pressure and provide porosity information.
Gas physisorption is considered non-selective, thus filling the surface step by step (or layer by layer) depending on the available solid surface and the relative pressure.
Filling the first layer enables the measurement of the surface area of the material because the amount of gas adsorbed when the mono-layer is saturated is proportional to the entire surface, that includes the internal and external surface.
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