Diathermic
Definition and meaning of Diathermic in chemistry.
Diathermic describes a material or system that allows heat to pass through it readily, permitting thermal energy to flow between a system and its surroundings until thermal equilibrium is reached.
In more detail
A diathermic (or diathermal) wall or boundary is the conceptual opposite of an adiabatic wall: it conducts heat efficiently rather than blocking it, so systems separated by a diathermic boundary exchange energy as heat until their temperatures equalize. This concept is central to the zeroth law of thermodynamics, which defines thermal equilibrium and temperature itself in terms of systems connected by diathermic walls. In practice, thin metal walls approximate diathermic behavior because metals are good thermal conductors, while insulating materials approximate adiabatic behavior.
Key facts
| Field | Physical Chemistry |
|---|---|
| Opposite term | Adiabatic (heat-blocking) |
| Key law | Zeroth law of thermodynamics |
| Typical example material | Thin metal (e.g., copper) walls |
A copper calorimeter wall is effectively diathermic: it allows heat released by a reaction inside the calorimeter to pass through and be absorbed by the surrounding water bath, enabling the temperature change to be measured accurately.
Frequently asked questions
What is the difference between diathermic and adiabatic?
A diathermic wall allows heat to pass through, so connected systems reach thermal equilibrium; an adiabatic wall blocks heat transfer entirely, so no heat exchange occurs regardless of temperature difference.
Why is the diathermic wall important in thermodynamics?
It underlies the zeroth law of thermodynamics, which states that two systems in thermal equilibrium with a third system (via diathermic walls) are in thermal equilibrium with each other, providing the logical basis for defining temperature.