Question

in the evaporator coil of an air - cooled air conditioner
refrigerant heats up as it changes from a liquid to a gas
refrigerant cools as it changes from a gas to a liquid
refrigerant cools as it changes from a liquid to a gas
refrigerant changes from a cool gas to a warm gas
refrigerant changes from a warm liquid to a cool liquid

Explanation:

In an air - cooled air conditioner's evaporator coil, the refrigerant undergoes a phase change from liquid to gas. During this evaporation process, it absorbs heat from the surrounding air, which cools the air. As it absorbs heat, the refrigerant itself heats up as it changes from a liquid to a gas.

Answer:

refrigerant heats up as it changes from a liquid to a gas