Entropy (?)

What is entropy ? A count of the number of equivalent states of a system Equivalent ? States ??

Entropy

 S < 0

Entropy

 S < 0

Entropy

 S > 0

Bonding/Assembly Bond Energy vs. Thermal Energy

What is Energy? Capacity to do Work. … What does this mean? Energy Stored (Potential) Chemical Nuclear Magnetic Electrostatic Mass EM Radiation Light X-rays microwaves Motion (Kinetic)

Energetics of an Explosion TNT In what form is the energy?

Energetics of an Explosion Bang! In what form is the energy?

Potential Energy U (or E)

F

Force, Energy and Bonding

A B

Free Energy Enthalpy and Entropy

Potential Energy x E b =bond energy x Transition State EbEb 0 E activ.

x Bonding / Assembling

x Disassociating

Potential Energy x EbEb x 0 Bonding / Assembling

Potential Energy x EbEb x 0 Disassociating

Effects of thermal energy on Bond Strength Potential Energy x EbEb kBTkBT Thermal Energy affects the Dissociation Constant and Bond Strength. Thermal Energy aids the dissociation of a bond. 0

Bond Strength: Boltzman Factor What is the probability that a bond will spontaneously dissociate???? P=e -E b /kT kT at room temperature = meV The rate of dissociation r d  e -E b /k B T Attempt frequency Vibrational frequency of bond or inverse relaxation time Probability per attempt Rate of dissociation

Force, Energy and Bonding

A B  U = U B –U A < 0 Spontaneous & Stable

Gibbs Free Energy G  S Thermodynamic Potential Helmholtz Free Energy F  U  S TempEntropy Enthalpy U + PV Potential Energy (chemical typically)

Thermodynamic Potential Helmholtz Free Energy F  U  S  F =  U - T  S When change in free energy is negative, process is spontaneous Define System

 F =  U – T  S  U = ? > or < 0 ?  S = ? > or < 0 ? When change in free energy is negative, process is spontaneous

Bond Strength: Boltzman Factor What is the probability that a bond will spontaneously dissociate???? P=e -E b /kT kT at room temperature = meV The rate of dissociation r d  e -E b /k B T Attempt frequency Vibrational frequency of bond or inverse relaxation time Probability per attempt Rate of dissociation

 U > or < 0 ?  S > or < 0 ?  F =  U - T  S

 U > or < 0 ?  S > or < 0 ?  F =  U - T  S

A B C D E Which representative state of the fiber has highest entropy?