1. Chapter 2
Some Concepts
Definitions

2. Definition of Thermodynamics
The science of energy and entropy
The science that deals with heat and work and those properties of substances that bear a relation to heat and work

3. Basis of thermodynamics
Experimental observations (findings)
Formalize into certain basic laws (zeroth, first, second, and third laws)

4. Objective of Student To gain both
a thorough understanding of the fundamentals, and
an ability to apply these fundamentals to thermodynamic problems

5. 2.1 Thermodynamic System and Control Volume
It contains matter and device(s) in a control surface.
Its boundaries may be closed (fixed mass/ control mass) or open ( involving a flow of mass), and may be movable or stationary.
It may have flows of energy in term of heat transfer and work across it.

6. Isolated system – No mass, heat, or work across the boundary.

7. Control Mass

8. Control Volume

9. 2.2 Macroscopic vs Microscopic Point of View
Macroscopic Point of View - concerned with the Gross or Average Effects of many molecules
Continuum
Microscopic Point of View - Classical and Statistical approach

10. 2.3 Properties and State of a Substance
Definition of a Phase
Phase is a quantity of matter that is homogeneous throughout.
Phase of a Substance
Substance may exist in a different state which involves observable and macroscopic properties
It may be regarded as a function of some statei, therefore Phasej = f (statei) = f(Pi, Ti , Densityi,…, etc. )
Factors, like Pi, Ti , Densityi,…, etc., are all properties of some statei.

11. Each property of a substance in a given state has only one(same) definite value.
Regardless of how the substance arrive at the state (path).
Thermodynamic Equilibrium Equilibrium is a state when system properties are invariable.

12. Thermodynamic Properties
Intensive Property
independent of mass, like P, T, and density
Extensive Property
varies directly with mass, like total volume Extensive properties per unit mass are intensive(specific) properties.

13. 2.4 Processes and Cycles Processes Cycles Path, i = j
Path of different states
Statei (Pi,Ti ,Di,.) to Statej (Pj,Ti ,Dj,.) , i≠j
Cycles
Path, i = j

14. Quasi-equilibrium process
A quasi-equilibrium process is one in which the deviation from thermodynamic equilibrium is infinitesimal.
Fig. 2.3

15. Quasi-equilibrium process
All the states the system passes through during a quasi-equilibrium process may be considered equilibrium states.
Many actual processes closely approach a quasi-equilibrium process and may be so treated with essentially no error.

16. 2.5 Units for Mass, Length, Time, and Force

17. 2.6 Energy An Important Concept
Definition： the capability to produce an effect
From molecular view, it can be transferred and stored.

18. Potential energy in the coordinate system for a diatomic molecule
Fig. 2.4

19. Heat transfer to water
Fig. 2.5

20. 2.7 Specific Volume and Density

21. The definition and continuum limit for the specific volume and (specific) densityρ=

22. Density of common substances

25. 2.8 Pressure
Fig. 2.8

26. Pressure Units Pascal ( Pa ) 1 Pa = 1 N/m2
bar 1 bar = 1x105 Pa = 0.1 MPa
atm 1 atm = Pa

27. Terms used in Pressure Measurement

28. Pressure measurement - using a column of fluid

30. 2.9 Equality of Temperature
Two bodies have equal temperature
if, when they are in thermal communication, no
change in any observable property occurs.

31. 2.10 The Zeroth Law of Thermodynamics
When two bodies have equality of temperature with a third body, they in turn have equality of temperature with each other.

32. 2.11 Temperature Scales Celsius scales oC Kelvin Scales K
Relation K = oC