Definitions for thermodynamics ref.

The following are some definitions the student should know in order to understand the language of thermodynamics.

System:  A defined physical space, whose boundaries usually correspond to some physical barrier or logical limit.  Examples

Isolated System:  A system which is entirely uninfluenced by changes outside the system.  In particular, there is no possibility of the transfer of either energy or matter across the boundaries of the system.   Detail

Closed System:  A system in which there is the possibility of energy exchange with the environment, but there is no transfer of matter across the boundaries.  This does not exclude the possibility of a change of internal composition due to chemical reaction.  Detail

Open Systems:  A system which can exchange both energy and matter with its environment. Detail
 

Summary of the three types of systems
Type of System: Ability to transfer energy between itself and the outside of the system Ability to transfer matter between itself and the outside of the system
Isolated System No transfer is possible No transfer is possible
Closed System Transfer is possible No transfer is possible
Open System Transfer is possible Transfer is possible
Universe:  Everything of importance which is outside the system in question.  This is sometimes thought of as an isolated system which includes another system which is being addressed.  Discussion

Surroundings:  That portion of the universe which does not include the system in question.  Thus, a universe consists of a system and its surroundings.

Spontaneous process:  A process which requires no influence from outside the system to proceed.  A process which can proceed in an isolated system.

Nonspontaneous process:  A process which does require influence from outside the system to proceed.  This process is impossible in an isolated system.

Equilibrium:  A condition in which there is no net change in any of the state functions of a system which has been allowed to arrive at rest with its surroundings.
 

Standard conditions 
For gases 1 atm pressure*
For solutes (ions) 1 M
For others 1 mole fraction

back to professor Condon's home page Back to Prof. Condon's home page                                                                                                                                                                                                      slides