Question #8ea79

1 Answer
Mar 17, 2015

You have three variables, P, V, and T, so you need a three-dimensional graph with P, V, and T 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 PV plane, you see the blue line hyperbola of Boyle's Law, PV=k.

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

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

Put them all together, and the 3D surface is a graph of the Combined Gas Law, PVT=k.