Why are two changes of state of the refrigerant necessary to operate a refrigerator?

The liquid refrigerant must evaporate (change from a liquid to a gas) and cool. This process releases heat. The cool gas is pumped through tubes so that it can absorb heat from the interior of the refrigerator, keeping it away from the food. Then the gas must condense into a liquid so that it can release the absorbed heat to the outside and begin the cycle again.