1. Physics I Overview of Fluids & Thermodynamics Prof. WAN, Xin xinwan@zju.edu.cn http://zimp.zju.edu.cn/~xinwan/

2. What have you learned?

3. Newton’s Second Law

4. Two-Block Problem

5. One, Two, Many

7. The Road Behind F Already learned: –Single-particle mechanics: translational and rotational variables –Two particles: center of mass + relative motion –Many particles: center of mass only F Fluids: gases, liquids

8. The Naïve Approach N particles r i (t), v i (t); interaction V(r i -r j )

9. A Simple Algorithm

10. MD Simulation (Argon) 100 K (above the boiling point)25 K (below the melting point)

11. Liquid Argon Freezing

12. Definitions F States of matter: phases –Gases: e.g., water vapor, oxygen –Liquids: e.g., water, blood, mercury –Solids: e.g., ice, glacier, rock, rubber “… physicist rejects the definition of a solid as (roughly) what hurts your toe when you kick it …” -- Concepts in Solids, by P.W. Anderson

13. Comparison of Phases SolidLiquidGas Compression Easy or difficult?

14. Comparison of Phases SolidLiquidGas CompressionDifficult Easy Tension Strong or not?

15. Comparison of Phases SolidLiquidGas CompressionDifficult Easy TensionStrongLimitedNo Shear force Sustainable or not?

16. Comparison of Phases SolidLiquidGas CompressionDifficult Easy TensionStrongLimitedNo Shear force Normally, sustainable Not sustainable Change shape? Easily or not?

17. Comparison of Phases SolidLiquidGas CompressionDifficult Easy TensionStrongLimitedNo Shear force Normally, sustainable Not sustainable Change shape? Normally, no Easily Intermolecular forces Strong or weak?

18. Comparison of Phases SolidLiquidGas CompressionDifficult Easy TensionStrongLimitedNo Shear force Normally, sustainable Not sustainable Change shape? Normally, no Easily Intermolecular forces Strong Relatively weak Very weak

19. By Rigidity F Fluids [Latin, to flow]: liquids & gases –Flow to take the shape of container F Normally, solids do not flow F Ch. 15. Statics: fluids at rest F Ch. 16. Dynamics: fluids in motion

20. By Interaction F Condensed matter: solids & liquids –(Almost) incompressible –Density changes little with temperature (at constant pressure) F Gases –Easily compressible –Density changes substantially with temperature (at constant pressure)

21. Gases

22. Liquids

23. Solids

24. Modern Notions F Gases: full symmetry -- disordered F Solids: reduced symmetry -- ordered –Think about snowflakes (hexagonal) F Liquids: short-range order only F Phase transitions –Disorder to order: symmetry breaking –Pioneered by Landau, Anderson, …

25. The Road Ahead F Questions to be answered –Newton’s laws for liquids (i.e., almost incompressible fluids)? –Compressible gases? –Microscope vs macroscope –Energy vs entropy (degree of disorder)

26. Plan F Fluid Statics F Fluid Dynamics F Basic concepts of Thermodynamics F The Kinetic Theory of Gases F The First Law of Thermodynamics F The Second Law of Thermodynamics F Phase Transitions