ChE Thermodynamics Lecture 1
8 February 2021
Introduction to Thermodynamics
Scope of Thermodynamics
Etymology:
Thermo – heat/energy
Dynamics – motion
*focus of thermodynamics: heat/energy
History of Thermodynamics
 1600s – notions of heat and temperature
 1700s – heat was a separate fluid-like substance
 1840s – Experiments of James Joule
 1850s – Heat is energy
 1824 – Sadi Carnot: idealized engine
 1850 – Rudolf Clausius and William Thomson (Kelvin) stated First Law of
Thermodynamics and Second Law of Thermodynamics
 1857 – Clausius revived the discussion of Daniel Bernoulli (1738) the idea that gases
consist of molecules in motion
 1860 – James Clerk Maxwell derived mechanics of individual molecular collisions the
expected distribution of molecular speeds of gases
 1860s – Clausius introduced entropy as ratio of heat and temperature
 Challenge: Second Law could not formally be derived from microscopic physics, but
somehow be a consequence of human inability to track large numbers of molecules
 1900 – Wilard Gibbs: statistical mechanics of systems of particles. He introduced the
notion of ensemble – a collection of many possible states of a system, each assigned a
certain probability
 1900s – development of thermodynamics was largely overshadowed by quantum theory
and little fundamental work was done in it
 1930s – the second law was generally regarded as a principle of physics whose
foundations should be questioned only as a curiosity
 1970s – Computer experiments; Charles Bennet laid groundwork for relating
computational and thermodynamic ideas
19th Century: Steam Engine
- The science of thermodynamics was developed
- Relationship of work produced to heat supplied
- Steam Engine: birth of thermodynamics
The First Law of Thermodynamics
- Energy is conserved
- Energy is neither created nor destroyed
- Energy appears in various forms and are functions of some recognizable and measurable
characteristics of the real world
The Second Law of Thermodynamics
- Entropy
System
- A particular region of space or body of matter under study
Surroundings
- Everything outside the system
System boundary
- Where the system and surrounds interact through transfer of material and energy
- Fixed or movable
Types of Systems:
 Open System – allows transfer of mass and energy into and out of the system
 Closed System – allows transfer of energy into and out of the system, but not mass
 Isolated System – does not allow transfer of mass and energy into and out of the system
“The state of a system must be described”
Two Possible Points of View: Macroscopic, Microscopic
Macroscopic
- Relates quantities such as composition, density, temperature, and pressure
-
Requires specification of a few fundamental measurable properties
Microscopic
- Depends on the existence and behavior of molecules
- Statistical mechanics – applies laws of quantum mechanics and classical mechanics to
large ensembles of atoms, molecules, or other elementary objects to predict and interpret
macroscopic behavior