<P> 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 . </P> <Ol> <Li> Every adiabat asymptotically approaches both the V axis and the P axis (just like isotherms). </Li> <Li> Each adiabat intersects each isotherm exactly once . </Li> <Li> 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). </Li> <Li> If isotherms are concave towards the north - east direction (45 °), then adiabats are concave towards the east north - east (31 °). </Li> <Li> 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). </Li> </Ol> <Li> Every adiabat asymptotically approaches both the V axis and the P axis (just like isotherms). </Li> <Li> Each adiabat intersects each isotherm exactly once . </Li>

In nature what is causing the increase in temperature and pressure