Composition phase diagrams are phase diagrams that also consider variations in composition of a mixture. The most classic of such diagrams are temperature-composition phase diagrams for binary alloys.
"Water" is the name for both:
- the chemical compound with chemical formula H2O
- the liquid phase of the chemical substance composed of the above chemical compound
Simplified phase diagram of water
. Source. Note the triple point and critical point visible. Phase diagrams are so cool!