# Entropy

## Entropy Is Additive

If two systems with entropy *S*_{1} and *S*_{2}, respectively, are brought into contact with each other, their combined entropy equals *S*_{1} + *S*_{2}. This is assured by the logarithmic relationship between *S* and *P*_{max}, as follows: If the number of microstates corresponding to the most likely distribution of the first system is *P*_{max1} and that of the second system is *P*_{max2}, then the number of possible microstates of the most likely distribution of the *combined* system is simply *P*_{max1}*P*_{max2}. It is a fundamental properties of **logarithms** that ln(*ab*) = ln(a) + ln(b), so if *S*_{1+2} is the entropy of the combined system, then

## Additional topics

- Entropy - Entropy Is Not Conserved
- Entropy - Entropy Is A Probabilistic Property
- Other Free Encyclopedias

Science EncyclopediaScience & Philosophy: *Electrophoresis (cataphoresis)* to *Ephemeral*Entropy - Entropy Is A Probabilistic Property, Entropy Is Additive, Entropy Is Not Conserved - Entropy measures disorder