The Open Door Web Site
HOME PAGE BIOLOGY CHEMISTRY PHYSICS ELECTRONICS HISTORY HISTORY of SCI & TECH MATH STUDIES LEARN FRENCH STUDY GUIDE PHOTO GALLERY
ATOMIC and NUCLEAR ELECTRICITY and MAGNETISM MEASUREMENTS MECHANICS OPTICS PRACTICAL WORK QUESTIONS RELATIVITY THERMAL PHYSICS WAVES
THERMAL PHYSICS
Google
Custom Search
Entropy and Disorder
At 0K (absolute zero) the atoms of a substance are stationary.  
They form a well ordered arrangement.  
If energy flows into the body, its atoms vibrate, they become a less well ordered arrangement.  
Energy entering a body increases disorder
Energy leaving a body decreases disorder
 
   
Ludwig Boltzmann showed that changes in entropy of a body can be considered as a direct measure of changes in the disorder of the arrangement of the particles.  
   
Consider a situation in which a hot body is brought into thermal contact with a cold body, for a short time.  
 
We will imagine that the quantity of energy, ΔQ, which flows from the hot to the cold body is so small that it does not significantly change the temperatures T1 and T2  
   
Each body will experience a change in the entropy of its particles.  
   
The hot body experiences a decrease in entropy (a negative change) of magnitude  
 
The cold body experiences an increase in entropy (a positive change) of magnitude  
 
The net change in entropy is  
 
and as T2 < T1 then  
 
   
Therefore, the net change in entropy due to this naturally occurring process must be greater than zero.  
   
This leads to the following statement of the second law of thermodynamics (see here for an alternative statement of the same law).  
   
The effect of naturally occurring processes is always to increase the total entropy (or disorder) of the universe.  
SITE MAP
WHAT'S NEW
ABOUT
PRIVACY
COPYRIGHT
SPONSORSHIP
DONATIONS
ADVERTISING
 

© The Open Door Team
2016
Any questions or
problems regarding
this site should be
addressed to
the webmaster

David Hoult 2017

Hosted By
Web Hosting by HostCentric

 
SiteLock
 
 
Thermal Physics Index Page