One of the important approach to the study of real gases involves the analysis of parameter Z called the compressibility factor Z = (PV_(m))/(RT) where P is pressure, V_(m) is molar volume, T is absolute temperature and R is the universal gas constant. such a relation can also be expressed as Z = ((V_(m)real)/(V_(m)ideal)) (where V_(m ideal) and V_(m real) are the molar volume for ideal and real gas respectively). Gas corresponding Z lt 1 have attractive forces amoung constituent particles. As the pressure is lowered or temperature is increased the value of Z approaches 1. (reaching the ideal behaviour) {:("Observation",,"Conclusion"),(I.Z =1,,I."The gas need not be showing the ideal behaviour"),(II. Zgt1,, II. "On applying pressure the gas will respond by"),(,,"increasing its volume"),(III. Z lt 1,, III. "The gas may be liquefied"),(IV. Z rarr1 "for low" P,, IV. "The gas is approaching the ideal behaviour") :}