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Introduction to Thermodynamics I

History of Thermodynamics: Various physic chemical changes that are occurring in nature areassociated with the exchange of energy. These energy changes are inthe form of heat light or sound. The energy changes that occurduring chemical changes are mainly in the form of heat energy. Thestudy of the heat exchanges during a chemical reaction is the basisfor thermodynamics.


Fundamentals ofThermodynamics: Thermodynamics deals with the energy changes thatoccur during a process. During physical and chemical changes one formof energy changes in to another.

Fundamentals ofthermodynamics depend majorly on three conventional terms- system,surrounding and boundary. Reaction taking place in open is calledopen system and the boundary is unlimited. When a reaction takesplace in closed container limiting only the contents to a containerbut the energy insulation is not done is termed to be closed systemwith open boundary. The system which can exchange neither the matternor the energy with surroundings is called isolated system.


General Thermodynamics:The general thermodynamics states that whenever there is a work doneon a system it is either by discharge of energy or by supply ofenergy. Water flows from a high point to a lower level with a forcewhich is a form of energy. The same force is to be applied to liftwater from a lower level to higher level. This exchange of energy isthe general explanation of thermodynamics.

Thermodynamic efficiency: Since no system is perfectly isolated from the surroundings and issealed in a boundary, there is some wasteful energy either in theperformance of a work or as a result of the work. The extent ofwastage varies in different conditions. This is called thethermodynamic efficiency.


Thermodynamics formulas: there are many formulas that are governing the thermodynamicprinciple. Based on the law of conservation of energy, the change ofinternal energy is the sum of the amount of heat supplied to thesystem and the work done by the system. ΔE= q + w

At constant pressure theenthalpy change ΔH = ΔE+ P ΔV


When the process involvesmultiple stages the change in enthalpy of the system is the sum ofthe different processes involved in it. This is called the Hess’slaw of constant heat summation. ΔH=ΔH1+ΔH2+ ΔH3……….+ΔHn

ΔG=ΔH - T ΔSwhere ΔS is the change inentropy.


Thermodynamics problems:1. If a system absorbs 6kJ of heat and delivers a work equivalent to9kJ by expanding, what is the value of change in internal energy (ΔG)of the system?

2. Prove that the productof pressure and volume has the dimension of energy.