Thermodynamic

Thermodynamic is a branch of physical and chemical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy),A thermodynamic system is a quantity of matter of fixed identity, around which we can draw a boundary. The boundaries may be fixed or moveable. Work or heat can be transferred across the system boundary. If a system is left undisturbed, it will eventually come to equilibrium and its properties will no longer vary with time.

The internal energy of a system (U) is the sum of the microscopic kinetic and potential energies of the particles. Ek, and Ep, respectively, with the microscopic kinetic and potential energy contributions to the internal energy where Q is the heat transferred between the surroundings and the system, and W is the work performed. The first Low of thermodynamics is the statement of the conservation of energy, which leads to the conclusion that the internal energy of any system is a function only of thermodynamic state U = Q. It means that heat and work are equivalent forms of energy according the following equation:

∆U + ∆Ek + ∆Ep = ±Q ± W

The Enthalpy, H

is a closely related quantity to the internal energy , it is defined as the internal energy plus the pressure–volume product, PV

dH = dU + d(PV )

For condensed systems the d(PV ) term is little then:

dH = dQ or ∆U = Q

The Entropy

The differential change in entropy for a closed system from one state to another is, by definition, directly proportional to the change in reversible heat, dQrev , and inversely proportional to the absolute temperature, T:

dS = dQrev/T

∆S = Q/T

∆S = ∆H/T

The Second Law of Thermodynamics

states that the entropy change of all processes must be positive. The entropy which increase as a system approaches equilibrium and is maximized at equilibrium .Such quantities are relatively easy to measure and permit the predication of the equilibrium state of any thermodynamic system.

Free Energy

The free energy (G) is defined base of the following equation:

G = H – TS or ∆G =∆ H – T∆S

The spontaneous occurrence of a natural event can be described in terms of a decrease in the appropriate free function. The free energy can occur base the following regel: