5. Capable of changing state under normal pressure changes.
Refrigerant is a fluid capable of changes of its state at very low temperatures. Released in atmospheric pressure refrigerants used in the appliance industry will boil at -15.34 degrees faherneiht changing its state from liquid to vapor. During this process from liquid to solid "Its evaporation process" the refrigerant will absorb large amounts of heat from the area being cooled.
6. Able to mix well with oil.
Where the refrigerant is essential for the cooling properties of a refrigeration system, the refrigeration oil is crucial for the correct functioning of the compressor. Lubricants for refrigeration compressors reduce friction, prevent wear and act as a seal between the high and low pressure sides.
Mixing with oil allows the refrigerant to pick up some of that oil and help it lubricate the compressor mechanical components. If a refrigerant does not carry some oil the compressor will eventually fail.
7. Non corrosive to metals.
Refrigerants need to be non corrosive - if they were they would damage the compressor and possible the tubing in the system. The system contains steel, "Compressor and Condenser" Copper "most tubing within the system and filter drier", and Aluminum "The evaporator".
8. Low flammability
Most refrigerants in appliances use R134a which is an A1 classification. This means it is not flammable, but does not mean it can not burn. This burning of refrigerants can cause hydrochloric and hydrofluoric acids which can damage compressor windings. On the other hand manufacturers are moving to R600 which is similar to R134a in temperature pressure relations but falls under the A3 classification which means it is very flammable.