Question #8ea79

1 Answer
Mar 17, 2015

You have three variables, PP, VV, and TT, so you need a three-dimensional graph with PP, VV, and TT axes.

You get a 3D surface that looks like the middle graph in the image below.

![Graph of a 3D surface from http://web.inc.bme.hu.](http://web.inc.bme.hu/csonka/csg/oktat/english/gaslaws_elemei/image001.gif)

If the temperature is constant and you look at the graph in a PVPV plane, you see the blue line hyperbola of Boyle's Law, PV = kPV=k.

If the pressure is constant and you look at the graph in a VTVT plane, you see the straight black line of Charles' Law, V= kTV=kT.

If the volume is constant and you look at the graph in a PTPT plane, you see the straight red line of Amontons' Law (often called Gay-Lussac's Law), P= kTP=kT.

Put them all together, and the 3D surface is a graph of the Combined Gas Law, (PV)/T = kPVT=k.