1. The problem statement, all variables and given/known data Which of the following are not extensive functions: S = (N/V)[S+[C][v] ln(T) + R ln(V)] S = (N)[S+[C][v] ln(T) + R ln(V/N)] S = ([N][/2])[S+[C][v] ln(T) + R ln(V/N)] 2. Relevant equations I'm not really sure how to approach this problem. The definition that I find for extensivity states: "At fixed pressure and temperature, if the amount of a substance N is changed by a factor λ, the volume V is also changed by the same factor" The corresponding example for the definition shows that if a system S(U,V,N) is combined with an identical system then the result should be 2U,2V,2N. First - I get hung up on the language of these statements quite often which is pretty discouraging. When the definition says "fixed temperature and pressure" and the forumlae have ln(T), how can I say that the system has a fixed temperature? Second - Should I be determining the extensivity by doubing S, for instance 2(S), or should I consider if in the formula for the system N and V scale by the same factor? 3. The attempt at a solution Once again, I'm not sure how to begin here. If someone could simply point me in the right direction it would be greatly appreciated.