Starting at Point A on the Phase Diagram (where CO2 coexists as a solid and liquid), if the pressure is steadily decreased all the way to 1.0 atm, but the temperature is maintained constant, what will happen to the CO2?
A) It will freeze into a solid
B) It will melt into a liquid
C) It will melt into a liquid which will then be converted into a gas
D) It will become a supercritical fluid
E) It will melt into a liquid but eventually converted into solid, gas, and liquid simultaneously
We’re basically being asked to determine the phase of the CO2 after the decrease in pressure at a constant temperature.
Recall that a phase diagram shows the transition of matter between solid, liquid, and gas phases as temperature and pressure changes.
In a phase diagram, the different phases can be identified by their location:
• Solid: can be found at high pressure and low temperature;
• Liquid: can be found between the solid and gas regions;
• Gas: can be found at low pressure and high temperature;