Positive or Negative Entropy Change

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Olivia Young 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

Positive or Negative Entropy Change

Postby Olivia Young 1A » Sat Feb 09, 2019 5:32 pm

When calculating the change in entropy, do you always have to analyze the heat flow to determine if it is positive or negative? So, if the surroundings gain heat while the system loses it, would deltaS of the system be negative and deltaS of the surroundings be positive?

705192887
Posts: 77
Joined: Fri Sep 28, 2018 12:18 am

Re: Positive or Negative Entropy Change

Postby 705192887 » Sat Feb 09, 2019 6:13 pm

Yes because if the system gives off heat, they are losing internal energy and there is a decrease in entropy (negative delta S). Vice versa for the surroundings.

Nathan Tran 4K
Posts: 92
Joined: Fri Sep 28, 2018 12:16 am

Re: Positive or Negative Entropy Change

Postby Nathan Tran 4K » Sat Feb 09, 2019 6:21 pm

I feel like there are a lot of ways to evaluate the change of signs for entropy--heat conventions is one of them, but because there are so many derivations of heat, you could also look at entropy change through different variables (this is good because then if you're not given heat or do not know how heat flows, you can evaluate things like the temperature, phase, etc.) However, because Delta S = - (Delta G - Delta H)/T and Delta S= Delta q/T and Delta S=Kbln (V2/V1), we need to understand that increasing one variable does not necessarily mean we can always tell the sign of entropy. The good part is we won't probably have too complicated systems, but for the most part, yes, entropy change can be viewed as in many lenses such as heat transfer.


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