Answer:
Gas
Increase the pressure
Explanation:
Let's refer to the attached phase diagram for CO₂ (not to scale).
<em>At -57 °C and 1 atm, carbon dioxide is in which phase?</em>
If we look at the intersection between -57°C and 1 atm, we can see that CO₂ is in the gas phase.
<em>At 10°C and 2 atm carbon dioxide is in the gas phase. From these conditions, how could the gaseous CO₂ be converted into liquid CO₂?</em>
Since at 10°C and 2 atm carbon dioxide is below the triple point, the only way to convert it into liquid is by increasing the pressure (moving up in the vertical direction).
