The First Law of Thermodynamics

1. The First Law of Thermodynamics One of the most fundamental manifestations in nature is the energy that accompanies all changes and transformations. The most common form form in which this energy appears, and the form to which all other tend, is heat. A study of this interrelation of the various forms of energy in a system constitutes the subject of thermodynamics.

2. Within any system the energy may be kinetic or potential in nature, or both. Kinetic energy is the energy a system possesses by virtue of its motion, be it molecular or motion of the body as a whole. Potential energy is the energy a system possesses by virtue of it’s position. i.e., energy due to structure of the body or due to its configuration with respect to other bodies. The absolute value of the total energy contained in a system: Einstein relation E = mc2,

3. The energies involved are so large that any changes in them as a result of the usual chemical or physical processes would be negligible compared with the totals. Further, the changes in the masses resulting from the energy transfers would be so small as to beyond detection by our available means of wheighing. Thermodynamics prefers to deal with energy differences which accompany changes in systems since these can be measured.

4. The energies involved are so large that any changes in them as a result of the usual chemical or physical processes would be negligible compared with the totals. Further, the changes in the masses resulting from the energy transfers would be so small as to beyond detection by our available means of wheighing. Thermodynamics prefers to deal with energy differences which accompany changes in systems since these can be measured.

5. A system is defined as any portion of the universe isolated in an inert container, which may be real or imaginary, for purpouses of study of the effect of various variables upon the contents of the system. The portion of the universe excluded from the system is called its surroundings. Open system can exchange both matter and energy with its surroundings. Isolated system <> Open system. Closed system is one in which no transfer of matter to or from surroundings is possible, but that of energy is.

6. A phase a homogeneous physically distinct mechanically separableportion of a system each phase can be separated from every other phase by such operations as a filtration, sedimentation, decantation, or any other mechanical means of separator It does not include, however, such separation methods as evaporation, distillation, adsorption or extraction. each phase may be continuous or it may be broken up into smaller portion

7. The phases present in a system may consist of pure substances or they may be solutions. A true solution is defined as a physically homogeneous mixture of two or more substances. This definition of a solution places no restriction on either the states of aggregationor relative amounts of the constituents. Homogeneoussystem contains only one phase. Heterogeneoussystem more than a single phase may be present, each phase is separated from every other by a phase boundary.

8. The properties of a system extensiveproperty of a system is any properly whose magnitude depends on the amount of substance present. Examples: total mass, volume and energy. intensiveproperties are those whose value is independent of the total amount, but depends instead on the concentration of the substance or substance in a system. Example: pressure, density, refractive index, and mass, volume, or energy per mole. The principle of reproducibility of states: the states of a system can be reproduced by reproducing the values of the variables

9. Partial Molal Quantities

10. at constant temperature and pressure: Euler’s theorem for homogeneous functions

11. Where : = 0 Gibss-Duhemequation: the partial molal quantities are not independent of each other, and that variation of the one partial molal quantity affects the others in the manner given by the equations.

12. slopes will be the values of at the selected concentrations.