Dear all, Generally as per physics the atom has nucleus over that electrons are spinning. I could n't imaging basic thermal terms with this physics. please clarify me. If i am wrong correct me. 1) i am confusing the term internal energy with electron spin. Is any relation there? 2) we defining enthalpy as useful energy(i.e. internal plus external pressure energy) and the entropy as dispersed energy and it cannot be used. What actually differs this two with respect to electron motion.? 3) Thermal conductivity of a material is based on the electron interaction. Electric conductivity also based on the same. But both are not proportional for all materials. Why? 4) We are telling the linear, rotational, vibration kinetic energies and potential energy of a molecule is increasing when doing heating, Is it a molecular phenomena or atomic phenomena? what is happening while adding latent heat then? 5) boiling point is depend on pressure. i.e. we restrict the molecular movement by applying external pressure so need more energy to overcome it, but the latent heat is less needed for high pressure medium to change its phase. Why? thanks in advance.