Isochore change of state

Isochoric change of state in the pV diagram

Isochore is a term used in thermodynamics . It describes a change in state of a substance during which its volume remains constant.

According to Amonton's law (also Gay-Lussac's 2nd law ) or the equation of state of an ideal gas , if the number of particles is also constant for an ideal gas:

Temperature and pressure in the pV diagram; note the isotherms have the same step size at constant volume

${\displaystyle {p \over T}=const.}$

It also follows that the relative change in pressure corresponds to the relative change in temperature :

${\displaystyle {p_{2} \over p_{1}}={T_{2} \over T_{1}}}$

• p ₁ : Absolute pressure before the supply of heat
• p ₂ : Absolute pressure after the application of heat
• T ₁ : temperature before the application of heat
• T ₂ : temperature after the application of heat

After the equation of state of an ideal gas does not is work done (no volume change!), According to the first law of thermodynamics ( ) comes with a supplied energy directly into the internal energy through: . ${\displaystyle \Delta U=\Delta Q+\Delta W}$ ${\displaystyle \Delta W=0}$ ${\displaystyle U}$ ${\displaystyle \Delta Q=\Delta U}$

In the pV diagram, an isochoric change in state has a vertical line, since only the pressure changes but not the volume.

See also

• Thermal equation of state of ideal gases

Web links

Commons : Isochoric processes  - collection of images, videos and audio files

Wiktionary: isochor  - explanations of meanings, word origins, synonyms, translations

• Visualization of the state changes with small interactive animations
• The general gas equation with diagrams and interactive animation