Question

What are the phase diagrams for water and `CO_2`?

Answer 1

If you just want the images of the phase diagrams, here they are (from Internet sources).

Notice the unusual solid-liquid equilibrium curve for water; this helps explain why solid ice floats in liquid water.

These diagrams also label the triple point and critical point for each substance (the region beyond the liquid-gas line is that of the supercritical fluid, where it is neither a distinct liquid nor gas).