CHAPTER XVI 



THE CONTINUITY AND CORRESPONDENCE OF 

 MOLECULAR STATES 



THE statement that matter is molecular in composi- 

 tion implies that no abrupt change takes place when 

 a body of matter undergoes a change from one to 

 another of the three forms solid, liquid, and aeri- 

 form. The changes in state are successive and con- 

 tinuous. Many attempts were made during the latter 

 half of the 19th century to formulate a relation which 

 would represent all the possible states not only of a 

 single substance but of all substances which are not 

 mixtures of several kinds of molecules. 



These equations were usually extensions of equation 

 (2) of page 164 which expresses the relation between 

 pressure, volume, and kinetic energy of translation, 

 the latter being a measure of the absolute temperature. 

 Let w represent the average change in the kinetic 

 energy of translation of a single molecule, when the 

 temperature of the mass is changed by one degree. 

 Then the average k.e. of translation of a single molecule 

 in a mass, which is at an absolute temperature of T, 

 will be wT. For N molecules the energy will beNwT. 



Hence PV = ~NwT (1) 



o 



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