The phase diagram of carbon dioxide illustrates its solid, liquid, and gaseous states under varying temperature and pressure conditions. Solid CO2 exists below -78.5°C at atmospheric pressure, liquid CO2 is present between 5.1 atm and 31.1°C, and gaseous CO2 is dominant above -78.5°C at 1 atm, with critical and triple points defining state transitions. The diagram also highlights the transitions between phases through sublimation, vaporization, and fusion lines.

1. Phase Diagram of Carbon Dioxide

2. • A phase diagram is a graphical representation
of the states of matter of a substance under
varying temperature and pressure.
• The phase diagram of carbon dioxide shows its
solid, liquid, and gaseous phases, along with
the triple and critical points.

3. • - Solid: Below -78.5°C at atmospheric pressure
• - Liquid: Exists between 5.1 atm and critical
temperature (31.1°C)
• - Gas: Dominates above -78.5°C at 1 atm
• - Critical Point: Beyond 31.1°C and 72.9 atm,
CO2 becomes a supercritical fluid
Triple Point: The point where all three phases (solid, liquid,
and gas) coexist. For CO₂, the triple point occurs at a
temperature of -56.6°C and a pressure of 5.11 atm.

4. Understanding the Regions
Solid Region:rigorous,fixed shape and volume.
Liquid Region:fixed volume,variable.
Gaseous Region: variable shape and volume.
Explanation of Transition Lines
Sublimation Line: Transition from solid to gas.
Vaporization Line: Transition from liquid to gas.
Fusion Line: Transition from solid to liquid.