Entropy Decrease: Sample Phenomena Explained

  • Thread starter Thread starter Domenicaccio
  • Start date Start date
  • Tags Tags
    decrease Entropy
Click For Summary
SUMMARY

Entropy can decrease locally within a system, such as a room with gas, as long as this decrease is offset by an increase in entropy elsewhere, maintaining the overall positive change in entropy. An air conditioner serves as a practical example, where it cools a space (decreasing local entropy) while increasing entropy in the surrounding environment. The Second Law of Thermodynamics states that the total entropy of an isolated system cannot decrease spontaneously, but local decreases are possible through the application of work. However, spontaneous decreases in entropy are not supported, as cooling a hot object does not require work to decrease its entropy.

PREREQUISITES
  • Understanding of the Second Law of Thermodynamics
  • Basic knowledge of thermodynamic systems
  • Familiarity with concepts of entropy and its measurement
  • Knowledge of heat transfer mechanisms
NEXT STEPS
  • Study the implications of the Second Law of Thermodynamics in various systems
  • Explore the principles of heat transfer, including conduction, convection, and radiation
  • Investigate real-world applications of entropy in refrigeration and air conditioning systems
  • Examine case studies of biological systems and their entropy management
USEFUL FOR

Students and professionals in physics, thermodynamics, and engineering, as well as anyone interested in the principles of energy transfer and entropy management in various systems.

Domenicaccio
Messages
86
Reaction score
0
Sorry but I suck at thermodynamics...

Can entropy decrease LOCALLY, provided that the decrease is compensated by an increase in the rest of the universe (or whatever isolated system we are in), so that the total change of entropy is positive?

Can you provide a sample phenomenon where this happens?
 
Science news on Phys.org
Yes, entropy can decrease locally at the expense of increased entropy elsewhere. An everyday example is an air conditioner.
 
temporarily yes...
take a room filled with gas.
the density in any small given sample volume of the room will have varying number of molecules, thus varying randomess, or entropy.
However the overall entropy of the isolated system (here, room) will be constant.
 
Yes- nearly all of biology/biochemistry works using this principle.
 
D H said:
Yes, entropy can decrease locally at the expense of increased entropy elsewhere. An everyday example is an air conditioner.

How easily can you guarantee that the entropy of a certain subsytem (e.g. an amount of water in a container) will be decreased by COOLING it?

(Obviously, the refrigerator would cause an entropy increase somewhere else)
 
to decrease entropy you must apply work, this work will coase an increase of entropy somewhere else. But I do not think there is an example of entropy decreasing spontaneously, unles you go back to the beginning of life (for which we cannot say exactly what happened)
 
bilha nissenson said:
to decrease entropy you must apply work, this work will coase an increase of entropy somewhere else. But I do not think there is an example of entropy decreasing spontaneously, unles you go back to the beginning of life (for which we cannot say exactly what happened)

This is completely wrong. Whenever a hot object cools, its entropy decreases. No work is necessary. There is no problem with the entropy of an object or a system decreasing spontaneously. What the Second Law forbids is the tendency for the total entropy in the universe to decrease spontaneously.
 

Similar threads

Undergrad Physics of paper absorbing Water -- Doesn't this decrease Entropy?
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Confusion about the entropy of mixing
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad How can the maximum entropy and minimum energy principles be physical?
  • · Replies 13 ·
Replies
13
Views
4K
High School Entropy change for reversible and irreversible processes
  • · Replies 12 ·
Replies
12
Views
3K
Stability and concavity of the entropy function
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad Is Entropy the inexorable conversion of potential to kinetic energy?
  • · Replies 17 ·
Replies
17
Views
3K
Why does the entropy of a closed system remain constant in a reversible process?
  • · Replies 10 ·
Replies
10
Views
3K
Show that entropy is a state function
  • · Replies 57 ·
2
Replies
57
Views
8K
Definition of a system in Boltzmann entropy
  • · Replies 1 ·
Replies
1
Views
1K
Graduate Equilibrium, entropy, probability - Release of constraints
  • · Replies 2 ·
Replies
2
Views
2K