Except an exchange of energy the substance can take part in physical and chemical processes. For management as them other level of internal energy of Ufr coinciding with the UT level at T=0K serves and the being lower than U Temperature coefficient of level of internal energy of Ufr is called as entropy of substance S:
The substance is characterized by weight. However as understanding of internal energy of substance U energy of its weight cannot serve. Only change of internal energy gives in to measurement. In modern physics it is considered to be that as there is a substance, there is also its internal energy, and change of this energy.
At increase in internal energy of substance at dU under the influence of warmth of dq, experience shows that dq is more than dU as at increase in internal energy the substance increases volume by the corresponding dV, thus, the part of energy goes for dw expansion work commission.
it is impossible to raise by usual multiplication of external pressure upon volume even if thus we come to the size proportional to energy. Work of pressure upon volume only brings a mistake in calculations therefore the concept of an enthalpy is serious in thermodynamics is not considered.
Substance in modern physical science it is accepted to mean elements of periodic system, or their connection as both the first, and the second have a constant chemical composition in the presence of external conditions of impact on them by concept. Any substance can be in a liquid, firm or gaseous state. The data set of elements and their connections in all aggregate states inherent in them form a matter. Any chosen substance and the next substance interacting with it (substances represent system.
Internal and free energy for many substances are measured in a wide interval. At 1000K U and G values for elements in a firm state make respectively: U = 13,1-33,7 kJ/mol, G =-17 —-83 kJ/mol.
The warmth which is distinguished both at fast and at slow cooling of fusion, it is impossible to use for change of internal energy of fusion. It emphasizes that fact that real processes proceed in the nature is energetically irreversible.
If between the chosen substance and environment there is a temperature gradient, there is a warmth – one of energy means of transport. After energy transfer we can speak only about energy of substance as the substance does not possess warmth.
At a constant temperature when pressure of system raises or goes down, internal energy of substance changes as well as in case of change of temperature: at increase – increases, at decrease – decreases. The energy transferred to substance at compression? is called as compression work, given at expansion – work of expansion (w).
At compression in the thermostat of the condensed substance branch of a quantity of warmth of dq is necessary for maintenance in it constant temperature. At the same time at compression internal energy of substance increases by dU.