18. Basic Laws and Concepts of Thermodynamics

yaboiemil's version from 2016-02-04 19:22

Basic Definitions

Question Answer
Classical ThermodynamicsNot concerned with the microstructure of the system. Considered a continuum.
Statistical ThermodynamicsConcerned with the microstructure of the system.
Isolated SystemExchange neither matter nor energy with surroundings
Closed systemExchange only energy with the surroundings
Open systemExchange matter and energy with the surroundings
State VariablesPhysical variables needed to describe a system. Remain at ZERO if a reversible thermodynamic cycle occurs.
Local or Intensive State VariablesVariables that remain identical throughout parts of the system (e.g. temp or pressure)
Extensive or Additive or Global State VariablesVariables that are valid for the whole system, sum of values for individual parts (internal energy or volume)


1. A Reversible Process is a process where the changes are infintesimal. If you reverse signs of changes, process is reversed.
2. Irreversible Process is a sequence of non-equilibrium states. A reversal of signs will not reverse the process, because some
of the variables were unknown or non equilibrium.
3. Work can be done on a system by surroundings, and the system can do work on its surroundings.

Mechanical Work in a System



Question Answer
ΔWWork Done
ΔsChange in position or trajectory
ASurface Area
ΔVChange in Volume


4. Negative work can occur, when the volume decreases, as the surroundings are doing work on the system
5. Positive work occurs when the system does work on the surroundings, and the volume increases.

Volume Work


6. The total work of a system from one V to another



7. Temperature and Heat is not the same thing.


Question Answer
TemperatureAverage kinetic energy of microscopic motions of a single particle.
HeatThe physical property that determines heat flow.
Heat flowThe flow of heat energy between 2 objects... Hotter to Colder.

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