Final answer:
To save time in refrigerant recovery, remove refrigerant in the liquid phase. The condenser in an air conditioner converts gas into liquid. Melting and vaporization are phase changes to a more energetic state.
Step-by-step explanation:
You can save time recovering the refrigerant from a system by removing as much as possible in the liquid phase. During the refrigerant recovery process, removing refrigerant in its liquid form is more time-efficient because liquids have a higher density compared to gases, and thus a greater quantity of refrigerant can be transferred in a shorter period. In contrast, when refrigerant is in the vapor phase, it occupies more volume and this makes the process slower.
The component of an air conditioner that converts gas into liquid is the condenser. It does this by condensing the gaseous refrigerant into a liquid, typically as it dissipates heat to the surrounding environment.
As for the phase changes where matter undergoes a transition to a more energetic state, these are melting and vaporization. When a substance melts, it goes from a solid to a liquid, and when it vaporizes, it transitions from a liquid to a gas.