## DS= q/T for surroundings or system?

$\Delta S = \frac{q_{rev}}{T}$

Miranda 1J
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

### DS= q/T for surroundings or system?

Can we use the equation DS = q/T for both the surroundings and the system?

Sohini Halder 1G
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Joined: Thu Jul 13, 2017 3:00 am
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### Re: DS= q/T for surroundings or system?

yep! So for instance, if heat is being released from System into Surroundings, System q will be negative and Surroundings q will be positive because the surroundings are absorbing heat. Further, System T should be higher than Surroundings T. These differing values will give you a different change in entropy value for the system versus the surroundings, unless its isothermal, which in that case it will just be opposite signs.

Emily Duggan 1F
Posts: 42
Joined: Fri Sep 29, 2017 7:07 am

### Re: DS= q/T for surroundings or system?

Yes, I believe we can use that equation for calculating both ∆S for a system or its surroundings, but you would have to make sure the sign of q on the numerator matches the situation correctly.