Chapter 8: second and third laws of thermodynamics

Spontaneous flow of heat is always unidirectional

From the higher to lower temperature

All naturally occurring processes always tend to

Change spontaneously in a direction which will lead to equilibrium

Heat cannot be converted to work

Without leaving permanent changes either in the systems involved or their surroundings

The entropy change of the substance must still be the same as it was in the reversible expansion

For it is determined by the reversible heat and not by the heat actually absorbed

An irreversible process occuring isothermally in an isolated system

Leads to an increase in the total entropy of the system

For any reversible process or cycle ,∆S=0

For any irreversible processes or cycle, ∆S >0

The second law of thermodynamics

All processes in nature tend to occur only with an increase in entropy and that the direction of change is always such as lead to the entropy increase

Clausius

“the energy of the universe is constant, the entropy of the universe tends to a maximum”

J.W. Gibbs

Entropy is a measure of “mixtupness” of a system

Entropy is a measure of the disorder in a system

2nd law’s essence

Stockpile of available energy in the universe is continually decreasing and is being converted into the disordered from of energy we call heat

T.W. Richards, Walter Nerst, Max Planck

Entropy of pure crystalline substances at the absolute zero of temperautre

Third law of Thermodynamics

Entropy of all pure crystalline solids may be taken as zero at the absolute zero temperature

Theoretical argument and experimental evidence showed that the entropy of solutions and supercooled liquids

Is not zero at 0K

for oure crystalline solid, the Law has been verified repeatedly