1. The problem statement, all variables and given/known data The internal energy of a system is expressed by function U(S.V)=S4/3Vα, where α is a constant. The value of α is? 3. The attempt at a solution Here internal energy is expressed in terms of volume and entropy but all the relations (as far as I know) are in terms of volume, entropy, mass and temperature or enthalpy. So how do you determine internal energy when pressure and mass are not given and everything else is a constant?