Editing Adiabatic process (section)

==Graphing adiabats==
[[Image:Entropyandtemp.PNG|thumb|upright=1.6|''P''–''V'' diagram with a superposition of adiabats and isotherms:
{{unordered list|item_style=margin-bottom: 0|The isotherms are the red curves and the adiabats are the black curves.
|The adiabats are isentropic.
|Volume is the horizontal axis and pressure is the vertical axis.}}]]
An adiabat is a curve of constant [[entropy]] in a diagram. Some properties of adiabats on a ''P''–''V'' diagram are indicated. These properties may be read from the classical behaviour of ideal gases, except in the region where ''PV'' becomes small (low temperature), where quantum effects become important.

# Every adiabat [[asymptotically]] approaches both the ''V'' axis and the ''P'' axis (just like [[isotherms]]).
# Each adiabat intersects each isotherm exactly once.
# An adiabat looks similar to an isotherm, except that during an expansion, an adiabat loses more pressure than an isotherm, so it has a steeper inclination (more vertical).
# If isotherms are concave towards the north-east direction (45° from V-axis), then adiabats are concave towards the east north-east (31° from V-axis).
# If adiabats and isotherms are graphed at regular intervals of entropy and temperature, respectively (like altitude on a contour map), then as the eye moves towards the axes (towards the south-west), it sees the density of isotherms stay constant, but it sees the density of adiabats grow. The exception is very near absolute zero, where the density of adiabats drops sharply and they become rare (see [[Nernst's theorem]]).{{clarify|reason=No quantitative formula is identified in that article as Nernst's theorem, only a qualitative "Impossibility Principle"|date=March 2015}}