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4. The Third Law Adiabatic Processes The Third Law of Thermodynamics Thermodynamics > The Third Law of Thermodynamics Free to share, print, make copies and changes. Get yours at www.boundless.com www.boundless.com/physics?campaign_content=book_5818_section_137&campaign_term=Physics&utm_campaign=powerpoint&utm_medium= direct&utm_source=boundless

5. Entropy is related to the number of possible microstates, and with only one microstate available at zero kelvin, the entropy is exactly zero. The third law of thermodynamics provides an absolute reference point for the determination of entropy. The entropy determined relative to this point is the absolute entropy. The Third Law Free to share, print, make copies and changes. Get yours at www.boundless.com www.boundless.com/physics/textbooks/alternative-to-physics-9th-john-d-cutnell-kenneth-w-johnson-1118129172- 9781118129173/thermodynamics-15/the-third-law-of-thermodynamics-137/the-third-law-506- 1644?campaign_content=book_5818_section_137&campaign_term=Physics&utm_campaign=powerpoint&utm_medium=direct&utm_source=bou ndless Temperature Entropy of Nitrogen View on Boundless.com Thermodynamics > The Third Law of Thermodynamics

6. Absolute entropy can be written as [Equation 1], where W is the number of available microstates. Thermodynamics > The Third Law of Thermodynamics Free to share, print, make copies and changes. Get yours at www.boundless.com www.boundless.com/physics/textbooks/alternative-to-physics-9th-john-d-cutnell-kenneth-w-johnson-1118129172- 9781118129173/thermodynamics-15/the-third-law-of-thermodynamics-137/the-third-law-506- 1644?campaign_content=book_5818_section_137&campaign_term=Physics&utm_campaign=powerpoint&utm_medium=direct&utm_source=bou ndless Equation 1 View on Boundless.com

7. Since at T=0 there is no entropy difference, an infinite number of steps in a thermodynamic cooling process is required to reach T=0. In adiabatic demagnetization cooling, energy transfers from thermal entropy to magnetic entropy (or disorder of the magnetic moments). The fact that T=0 cannot be achieved in reality is a direct consequence of the third law of thermodynamics. Adiabatic Processes Free to share, print, make copies and changes. Get yours at www.boundless.com www.boundless.com/physics/textbooks/alternative-to-physics-9th-john-d-cutnell-kenneth-w-johnson-1118129172- 9781118129173/thermodynamics-15/the-third-law-of-thermodynamics-137/adiabatic-processes-507- 1127?campaign_content=book_5818_section_137&campaign_term=Physics&utm_campaign=powerpoint&utm_medium=direct&utm_source=bou ndless Can Absolute Zero be Reached? View on Boundless.com Thermodynamics > The Third Law of Thermodynamics

8. Free to share, print, make copies and changes. Get yours at www.boundless.com Appendix

9. Key terms absolute zero The coldest possible temperature: zero on the Kelvin scale and approximately -273.15°C and -459.67°F. The total absence of heat; the temperature at which motion of all molecules would cease. degeneracy Two or more different quantum states are said to be degenerate if they are all at the same energy level. demagnetization The process of removing the magnetic field from an object. isentropic Having a constant entropy. microstate The specific detailed microscopic configuration of a system. Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics

10. Can Absolute Zero be Reached? Temperature-Entropy diagram. Horizontal lines represent isentropic processes, while vertical lines represent isothermal processes. Left side: Absolute zero can be reached in a finite number of steps if S(T=0,X1)≠S(T=0, X2). Right: An infinite number of steps is needed since S(0,X1)= S(0,X2). Free to share, print, make copies and changes. Get yours at www.boundless.com Wikipedia. "Third law of thermodynamics." GNU FDL http://en.wikipedia.org/wiki/Third_law_of_thermodynamics View on Boundless.comGNU FDLhttp://en.wikipedia.org/wiki/Third_law_of_thermodynamicsView on Boundless.com Thermodynamics

11. Temperature Entropy of Nitrogen Temperature–entropy diagram of nitrogen. The red curve at the left is the melting curve. Absolute value of entropy can be determined shown here, thanks to the third law of thermodynamics. Free to share, print, make copies and changes. Get yours at www.boundless.com Wikipedia. "Entropy (classical thermodynamics)." CC BY http://en.wikipedia.org/wiki/Entropy_%2528classical_thermodynamics%2529 View on Boundless.comCC BYhttp://en.wikipedia.org/wiki/Entropy_%2528classical_thermodynamics%2529View on Boundless.com Thermodynamics

12. Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics On what idea did Nernst support that entropy could be a nonzero constant at absolute zero? A) Isentropic process B) Isothermal expansion C) Degeneracy D) Phase transitions

13. Free to share, print, make copies and changes. Get yours at www.boundless.comwww.boundless.com Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/CC BY-SA 3.0http://www.boundless.com/ Thermodynamics On what idea did Nernst support that entropy could be a nonzero constant at absolute zero? A) Isentropic process B) Isothermal expansion C) Degeneracy D) Phase transitions

14. Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics Given that Bolzmann's constant is 1.3806488 × 10-23 m2 kg s-2 K- and there are 3 microstates, what is the absolute entropy of the system? A) 1.3806488 x 10-23 B) 0 C) 4.1419464 x 10-23 D) 1.5167977 x 10-23

15. Free to share, print, make copies and changes. Get yours at www.boundless.comwww.boundless.com Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/CC BY-SA 3.0http://www.boundless.com/ Thermodynamics Given that Bolzmann's constant is 1.3806488 × 10-23 m2 kg s-2 K- and there are 3 microstates, what is the absolute entropy of the system? A) 1.3806488 x 10-23 B) 0 C) 4.1419464 x 10-23 D) 1.5167977 x 10-23

16. Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics What causes the cooling in adiabatic demagnetization cooling? A) Magnetic fields slow the movement of atoms, which causes a temperature decrease B) Thermal energy used to create order of magnetic moments cause a temperature decrease C) Magnetic fields adiabatically increasing cause a temperature decrease D) Thermal energy used to cause disorder of magnetic moments causes a temperature decrease

17. Free to share, print, make copies and changes. Get yours at www.boundless.comwww.boundless.com Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/CC BY-SA 3.0http://www.boundless.com/ Thermodynamics What causes the cooling in adiabatic demagnetization cooling? A) Magnetic fields slow the movement of atoms, which causes a temperature decrease B) Thermal energy used to create order of magnetic moments cause a temperature decrease C) Magnetic fields adiabatically increasing cause a temperature decrease D) Thermal energy used to cause disorder of magnetic moments causes a temperature decrease

18. Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics How does entropy behave at absolute zero? A) Entropy is a constant at all temperatures B) Entropy increases drastically C) Entropy is highly unstable, cycling between very high and very low values D) Entropy is at its minimum value

19. Free to share, print, make copies and changes. Get yours at www.boundless.comwww.boundless.com Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/CC BY-SA 3.0http://www.boundless.com/ Thermodynamics How does entropy behave at absolute zero? A) Entropy is a constant at all temperatures B) Entropy increases drastically C) Entropy is highly unstable, cycling between very high and very low values D) Entropy is at its minimum value

20. Attribution Wikipedia. "Magnetic refrigeration." CC BY-SA 3.0 http://en.wikipedia.org/wiki/Magnetic_refrigerationCC BY-SA 3.0http://en.wikipedia.org/wiki/Magnetic_refrigeration Wiktionary. "isentropic." CC BY-SA 3.0 http://en.wiktionary.org/wiki/isentropicCC BY-SA 3.0http://en.wiktionary.org/wiki/isentropic Wiktionary. "demagnetization." CC BY-SA 3.0 http://en.wiktionary.org/wiki/demagnetizationCC BY-SA 3.0http://en.wiktionary.org/wiki/demagnetization Wiktionary. "absolute zero." CC BY-SA 3.0 http://en.wiktionary.org/wiki/absolute+zeroCC BY-SA 3.0http://en.wiktionary.org/wiki/absolute+zero Wikipedia. "Third law of thermodynamics." CC BY-SA 3.0 http://en.wikipedia.org/wiki/Third_law_of_thermodynamicsCC BY-SA 3.0http://en.wikipedia.org/wiki/Third_law_of_thermodynamics Wikipedia. "Third law of thermodynamics." CC BY-SA 3.0 http://en.wikipedia.org/wiki/Third_law_of_thermodynamicsCC BY-SA 3.0http://en.wikipedia.org/wiki/Third_law_of_thermodynamics Wikipedia. "degeneracy." CC BY-SA 3.0 http://en.wikipedia.org/wiki/degeneracyCC BY-SA 3.0http://en.wikipedia.org/wiki/degeneracy Wiktionary. "microstate." CC BY-SA 3.0 http://en.wiktionary.org/wiki/microstateCC BY-SA 3.0http://en.wiktionary.org/wiki/microstate Wiktionary. "absolute zero." CC BY-SA 3.0 http://en.wiktionary.org/wiki/absolute+zeroCC BY-SA 3.0http://en.wiktionary.org/wiki/absolute+zero Free to share, print, make copies and changes. Get yours at www.boundless.com Thermodynamics