Second law equation


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JonathanS 1H
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

Second law equation

Postby JonathanS 1H » Sun Feb 09, 2020 5:55 pm

Hello everyone
Can someone explain the second law of thermodynamics in relation to the equation (delta)S = qrev / T? I am confused as to what this equation means in a conceptual sense.

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Second law equation

Postby Alice Chang 2H » Sun Feb 09, 2020 6:24 pm

ΔS : change in entropy
q(rev) : heat inputted into the system that is reversible
T : temperature

This equation is a "basic way of evaluating ΔS for constant-temperature processes such as phase changes, or the isothermal expansion of a gas."
So by dividing heat inputted into the system by the constant temperature that the system is held at, you can find the amount of disorder (entropy) of a system.

Hope this helps!

JonathanS 1H
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

Re: Second law equation

Postby JonathanS 1H » Sun Feb 09, 2020 6:30 pm

I guess my question is more of how does this equation prove that entropy always increases in a system.

405268063
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

Re: Second law equation

Postby 405268063 » Sun Feb 09, 2020 7:40 pm

I don't think that this equation shows that entropy always increases in a system. I think during the review session today, we were told to use this only for phase changes.


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