DS= q/T for surroundings or system?

[Miranda 1J]

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

[Sohini Halder 1G]

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]

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.