Entropy Decrease: Sample Phenomena Explained

In summary, entropy can decrease locally at the expense of increased entropy elsewhere, as seen in the example of an air conditioner. However, this decrease in entropy requires work and ultimately leads to an overall increase in entropy in the universe. One exception to this is in biology and biochemistry, where entropy can decrease locally without an increase elsewhere. Cooling a subsystem, such as water in a container, can also decrease its entropy without requiring work, but this will lead to an increase in entropy elsewhere. The Second Law of Thermodynamics forbids a spontaneous decrease in the total entropy of the universe.
  • #1
Domenicaccio
86
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
  • #2
Yes, entropy can decrease locally at the expense of increased entropy elsewhere. An everyday example is an air conditioner.
 
  • #3
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.
 
  • #4
Yes- nearly all of biology/biochemistry works using this principle.
 
  • #5
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)
 
  • #6
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)
 
  • #7
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.
 

1. What is entropy decrease?

Entropy decrease refers to the decrease in the amount of disorder or randomness in a system. It is a measure of the amount of energy that is unavailable for work in a system.

2. What are some examples of phenomena that demonstrate entropy decrease?

Some examples of phenomena that demonstrate entropy decrease include the freezing of water into ice, the formation of crystals, the condensation of gas into liquid, and the organization of a living organism.

3. How is entropy decrease related to the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This is because energy tends to disperse and become more evenly distributed, resulting in an increase in disorder. However, in certain cases, such as the examples mentioned above, localized decreases in entropy can occur.

4. Can entropy decrease be reversed?

Yes, entropy decrease can be reversed. This is known as a decrease in entropy, and it requires an input of energy. For example, melting ice or boiling water can reverse the entropy decrease that occurred during freezing or condensation.

5. What are the implications of entropy decrease for living organisms?

Entropy decrease is essential for the functioning and survival of living organisms. In order to maintain their internal organization and carry out metabolic processes, living organisms constantly take in energy and create localized decreases in entropy. However, this also means that living organisms contribute to the overall increase in entropy in the universe, as they release energy and waste products into their surroundings.

Similar threads

I Physics of paper absorbing Water -- Doesn't this decrease Entropy?
    • Thermodynamics
Replies
1
Views
903
I Confusion about the entropy of mixing
    • Thermodynamics
Replies
3
Views
1K
I How can the maximum entropy and minimum energy principles be physical?
    • Thermodynamics
Replies
13
Views
1K
B Entropy change for reversible and irreversible processes
    • Thermodynamics
Replies
12
Views
1K
I Is Entropy the inexorable conversion of potential to kinetic energy?
    • Thermodynamics
Replies
17
Views
1K
Stability and concavity of the entropy function
    • Thermodynamics
Replies
3
Views
2K
Why does the entropy of a closed system remain constant in a reversible process?
    • Thermodynamics
Replies
10
Views
1K
Show that entropy is a state function
    • Thermodynamics
2
Replies
57
Views
6K
Definition of a system in Boltzmann entropy
    • Thermodynamics
Replies
1
Views
728
A Equilibrium, entropy, probability - Release of constraints
    • Thermodynamics
Replies
2
Views
842

Hot Threads

Recent Insights

Back
Top