isotermiset

Isotermiset is a Finnish term used to describe phenomena, processes, or conditions in which temperature remains constant. The word derives from iso- meaning equal and terminen meaning relating to temperature. In scientific contexts, isotermiset describes either the state of a system or the course of a process conducted at a fixed temperature.

In thermodynamics, an isothermal process maintains a constant temperature throughout. For an ideal gas, this yields PV = nRT with T constant; the work done during a change is W = nRT ln(V2/V1), and the heat exchanged equals W. Real systems may require heat transfer to surroundings to maintain the temperature, and deviations from ideal gas behavior become relevant at high pressures or near phase transitions.

Isothermal conditions are commonly used in laboratory experiments, calorimetry, and chemical kinetics where precise temperature control is essential. They are also relevant in materials engineering, food processing, fermentation, and other industrial processes where maintaining a fixed temperature helps isolate thermal effects from mechanical or chemical factors. In geoscience and meteorology, isotherms describe lines or layers of equal temperature on maps or in subsurface profiles, reflecting spatial temperature distributions.

Related concepts include isothermal, isotherm, adiabatic, isobaric, and isochoric processes, which describe different ways temperature, pressure, and volume can change. Isotermiset should be understood within the broader framework of thermodynamics and heat transfer, and they are primarily a description of constant-temperature conditions across various disciplines.