negative entropy  [ENDORSED]


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Felicia Fong 2G
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negative entropy

Postby Felicia Fong 2G » Sun Feb 04, 2018 12:32 pm

Does a negative entropy mean no disorder?

Srbui Azarapetian 2C
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Re: negative entropy

Postby Srbui Azarapetian 2C » Sun Feb 04, 2018 12:45 pm

The change in entropy can be negative, and when this is the case, you can think of it as a system becoming more ordered. An example would be of condensation, in the transition from a gas (high entropy state) to a liquid (low entropy state).

Fatima_Iqbal_2E
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Re: negative entropy

Postby Fatima_Iqbal_2E » Sun Feb 04, 2018 12:48 pm

The formula used to determine entropy, S= lnW requires that W be a positive number, since you can't have a negative number of microstates, and thus, can't have a negative degeneracy. Because of this, I don't think there is any way that you'd be able to have a system with a negative entropy.

Ridhi Ravichandran 1E
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Re: negative entropy

Postby Ridhi Ravichandran 1E » Sun Feb 04, 2018 4:56 pm

There is no such thing as negative entropy, but a negative change in entropy exists. For example, a reaction that condenses from a gas to liquid would have a negative delta S because the liquid would occupy less possible states than the gas due to the decrease in temperature and volume.

ZoeHahn1J
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Re: negative entropy

Postby ZoeHahn1J » Sun Feb 04, 2018 7:40 pm

Entropy must practically always be positive, since S approaches 0 as T approaches 0. The third law of thermodynamics holds that "The entropies of all perfect crystals approach zero as the absolute temperature approaches zero."

Sarah Clemens 1B
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Re: negative entropy

Postby Sarah Clemens 1B » Mon Feb 05, 2018 12:44 am

A negative entropy just means that the system is becoming more ordered, it doesn't mean that there isn't any entropy.

Caroline LaPlaca
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Re: negative entropy

Postby Caroline LaPlaca » Mon Feb 05, 2018 9:59 am

no, it just means the system is becoming more ordered.

Wenjie Dong 2E
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Re: negative entropy

Postby Wenjie Dong 2E » Mon Feb 05, 2018 12:11 pm

There is no such thing as negative entropy. The negative delta entropy means a decrease in disorder.

Shanmitha Arun 1L
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Re: negative entropy

Postby Shanmitha Arun 1L » Mon Feb 05, 2018 12:39 pm

Look at the signs in entropy as a change rather than positive and negative entropy.

Alex Nechaev 1I
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Re: negative entropy  [ENDORSED]

Postby Alex Nechaev 1I » Mon Feb 05, 2018 2:17 pm

Negative entropy simply means that there is a decrease in disorder, or rather an increase in order of the system.

McKenna disc 1C
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Re: negative entropy

Postby McKenna disc 1C » Mon Feb 05, 2018 2:54 pm

I think an important delineation to make is whether or not you're referring to entropy (S) or change in entropy (ΔS).
Entropy in its absolute value is calculated by using the Boltzmann equation, S= k ln W. In terms of entropy in its absolute value (calculated through the previous equation), no, negative entropy does not exist. A system either has no disorder (which results in a 0 value for S), or some disorder (which results in a positive value for S).
But, I think your question here involves calculating change in entropy, aka the second law of Thermodynamics, ΔS= -qrev/T. In this scenario, it is perfectly acceptable for the obtained value to be negative-- as many other people in this thread have already clarified, that just indicates that the system is becoming more ordered through whatever change is taking place.


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