Answer
Solid $\rightarrow$ liquid $\rightarrow$ gas
Work Step by Step
$Fig. 11.39(b)$ shows that $CO_2$ solid held at 20 atm moves towards the liquid phase and then the gaseous phase when temperature is increased and pressure is kept constant.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.