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Entropy (?)

Entropy (?). What is entropy ?. A count of the number of equivalent states of a system Equivalent ? States ??. Entropy. Entropy. D S < 0. Entropy. Entropy. D S < 0. Entropy. Entropy. D S > 0. Bonding/Assembly. Bond Energy vs. Thermal Energy. What is Energy?.

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Entropy (?)

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  1. Entropy (?)

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

  3. Entropy

  4. Entropy DS < 0

  5. Entropy

  6. Entropy DS < 0

  7. Entropy

  8. Entropy DS > 0

  9. Bonding/Assembly Bond Energy vs. Thermal Energy

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

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

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

  13. Potential Energy U (or E)

  14. Potential Energy U (or E) F

  15. Force, Energyand Bonding

  16. Force, Energyand Bonding A B

  17. Free EnergyEnthalpy and Entropy

  18. x Potential Energy Transition State Eactiv. 0 x Eb Eb=bond energy

  19. Bonding / Assembling x

  20. Disassociating x

  21. Bonding / Assembling x Potential Energy 0 x Eb

  22. Disassociating x Potential Energy 0 x Eb

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

  24. Bond Strength: Boltzman Factor What is the probability that a bond will spontaneously dissociate???? kT at room temperature = 0.025 meV P=e-Eb/kT The rate of dissociation rd = we-Eb/kBT Rate of dissociation Attempt frequency Vibrational frequency of bond or inverse relaxation time Probability per attempt

  25. Force, Energyand Bonding

  26. Force, Energyand Bonding A B DU = UB –UA < 0 Spontaneous & Stable

  27. Thermodynamic Potential Gibbs Free Energy G = H - TS Enthalpy U + PV Temp Entropy Helmholtz Free Energy F = U - TS Potential Energy (chemical typically)

  28. Thermodynamic Potential Helmholtz Free Energy F = U- TS DF=DU- TDS Define System When change in free energy is negative, process is spontaneous

  29. DF=DU– TDS DU = ? > or < 0 ? DS = ? > or < 0 ? When change in free energy is negative, process is spontaneous

  30. Bond Strength: Boltzman Factor What is the probability that a bond will spontaneously dissociate???? kT at room temperature = 0.025 meV P=e-Eb/kT The rate of dissociation rd = we-Eb/kBT Rate of dissociation Attempt frequency Vibrational frequency of bond or inverse relaxation time Probability per attempt

  31. DU > or < 0 ? DS > or < 0 ? DF=DU- TDS

  32. DU > or < 0 ? DS > or < 0 ? DF=DU- TDS

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

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