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Entropy

I don't fink you can find a good explanation. It is one of those concepts that are well defined mathematically but still almost impossible grasp,
Entropy is usually described as "the amount of disorder in the system", it is not a good description but it is probably the best one you can get.

Thermodynamics is without doubt the most difficult field in classical physics, personally I think quantum mechanism is easier to understand.
 
If you want I have a thermodynamics text I'll sell you ;0) Ah well, I'll take a shot.

In a perfect world any system would be perfectly reversible. That is you could go from point A to point B back and forth as long as you like. However in practice some ammount of energy is always lost as heat. This is called entrophy. Eventually entrophy will reach a point where the whole universe is the same temp and as a result no work can be done.
 
Originally posted by: f95toli
I don't fink you can find a good explanation. It is one of those concepts that are well defined mathematically but still almost impossible grasp,
Entropy is usually described as "the amount of disorder in the system", it is not a good description but it is probably the best one you can get.

Thermodynamics is without doubt the most difficult field in classical physics, personally I think quantum mechanism is easier to understand.
Click to expand...

I wouldn't say that...basically there are two driving forces in the world, (1)the drive to go from higher energy to lower energy and (2)the drive to go from order to disorder.

All chemical reactions hinge on these two effects.
 
True, but that still does not explain what entropy IS.
I undestand the mathematical definition and I can use the concept to calculate things, but still I can not explain what it is, it is a strange concept.
I have the same problem with the concept of temperature, this is another concept which is almost impossible to define (as far as I know there IS no definition of temperaure so I am not alone).
 
Originally posted by: f95toli
True, but that still does not explain what entropy IS.
I undestand the mathematical definition and I can use the concept to calculate things, but still I can not explain what it is, it is a strange concept.
I have the same problem with the concept of temperature, this is another concept which is almost impossible to define (as far as I know there IS no definition of temperaure so I am not alone).
Click to expand...

Temperature is the ratio of excited QM states to unexcited states. If 100% of your electrons are in unexcited states, that corresponds to absolute zero.

Think of it this way: you have a can full of marbles. At first you shake it gently (low temperature), so pretty much all the marbles are at the bottom, with a couple of them bouncing up a bit, every once in a while. As you shake it harder and harder, more and more marbles start to bounce to higher points in the can. If you shake the can as hard as possible (actually, harder than possible for T->infinity), the marbles are equally likely to be at any height in the can. Infinite temperature corresponds to all states being equally occupied.

Entropy really isn't that strange a concept once you realize that it really IS just the amount of order/disorder, and that the trend is to increase OVERALL disorder (so entropy can go down in some processes, but it has to go up by a higher amount in a different process)
 
How does something get driven to disorder from order? Isn't equallibrium perfect once attained? Life is probably an unusual example for order to disorder, though.
 
The butterfly effect is a good analogy of Entropy.

As some force expells a degree of energy onto it's environment, that energy is certain to go somewhere. As one thing affects the next, the amount of "disorder" or variables is favored to grow.

This is why it's becomes increasingly difficult to increase order. Mathematically it seems that you can't return to the same point once things increase exponentially.
It's often likened to sugar dissolving in water. You can't extract the sugar back into it's previous state.

I like to think of Entropy less as disorder and more as the scenario of constant change.
 
In relation to molecules, entropy is often applied to as the tendency for molecules to become "orderly" and disperse to a less concentrated area.
 
I study physics and I'm intrigued as well.
A professor told me entropy indeed gives an idea of the disorder of a system and is computable! It's a number! A computable quantity. Just take the log of the number of possible ways in which energy can be distributed.
If your energy can only be distributed in one way, you have entropy 0, perfect order.. 🙂

Maybe this helps. Good luck in your quest!
 
jagec: Yes and no. The problem is that this "definition" of temperature does not cover everything.
As long as you can work with "regular" distribution functions (Boltzamnn, Fermi, Bose-Einsten) it works but when you are dealing with very low termperatures (below say 1 mK) or with very few particles the definition breaks down

When I took a course in low-temperature physics a few years ago the professors (who has been working in the field of low-temperature physics for 40 years and has worked on temperature standards) told us that he had never seen a good definition and as far as he knew it did not exist. At the time I did not really belive him but now I have been working on the same field myself for some time and I can assure you he was right. There are a number of books on the subject that are quite interesting.
 
i find it funny/twisted that the state of optimized entropy would be perfectly homogeneous. of course, infinite entropy cant be reached until every particle in the universe is infinitely far apart, but obviously that is just theoretical. also gets me to start thinking, would perfect entropy mean every particle in teh universe would en an evenly and infinitely spaced hydrogen atom? or is the pairing of 1 proton and 1 electron a higher energy state than having them seperate with all the potential energy of combining? it's prolyl not a mystery, just an answer i dont know
 
*yawn*

There is no entropy. Every atom is behaves exactly as it should, in a predictable and logical manner.
I don't think an ozone molecule would say he's acting erratically. 🙂
 
Best definition of zero entropy is a college freshman. They seek the state of lowest energy and most disorganization.
 
Originally posted by: JediJeb
Best definition of zero entropy is a college freshman. They seek the state of lowest energy and most disorganization.
Click to expand...

"zero entropy" is MORE order, not less...

Originally posted by: f95toli
jagec: Yes and no. The problem is that this "definition" of temperature does not cover everything.
As long as you can work with "regular" distribution functions (Boltzamnn, Fermi, Bose-Einsten) it works but when you are dealing with very low termperatures (below say 1 mK) or with very few particles the definition breaks down
Click to expand...

true, but it's a start. Like most models in science, it breaks down in the outer limits but does all right in the middle.
 
oops I knew I would get that quote wrong, my thermodynamics professor used to tell that one and I never could get it right 🙂
 
I've heard that entropy is at a maximum inside of a black hole.

Think of entropy like taking a box with a layer of colored marbles in the bottom, say three marbles of three colors, red, green, and blue.

Now shake the box.

It's very likely that the marbles will not be in the same order when you get done. It would take many shakes to get them back into that order.
 
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