Isotherm
Definition and meaning of Isotherm in chemistry.
An isotherm is a curve or process that occurs at constant temperature. In chemistry, isotherms most commonly describe adsorption phenomena, showing how much material adsorbs onto a surface as a function of pressure or concentration at a fixed temperature.
In more detail
The term combines iso (same) and therm (temperature). In thermodynamics, an isothermal process maintains constant temperature during expansion, compression, or other changes. In surface and analytical chemistry, adsorption isotherms are graphs showing equilibrium between an adsorbate and adsorbent surface at a specific temperature. The shape of an isotherm reveals surface area, porosity, and adsorption mechanisms, making isotherms essential for material characterization and separation process design.
Key facts
| Field | Physical Chemistry |
|---|---|
| Etymology | iso (same) + therm (heat/temperature) |
| Primary use | Adsorption studies and material surface characterization |
| Common models | Langmuir, Freundlich, BET |
A nitrogen adsorption isotherm measured at 77 K is widely used to determine the surface area of porous materials using the Brunauer-Emmett-Teller (BET) method.
Frequently asked questions
Why are adsorption isotherms important in chemistry?
They reveal critical material properties such as surface area and pore structure, essential for gas separation, water purification, catalysis, and other applications.
What is the difference between an isotherm and an isobar?
An isotherm represents constant temperature, while an isobar represents constant pressure. Each describes different equilibrium conditions.