9.3

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Gabriela Carrillo 1B
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

9.3

Why is energy negative in the first calculation of entropy (-40000J/800K) and positive in the second (40000J/200K)?

Ashin_Jose_1H
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Re: 9.3

Heat is being transferred from one reservoir to another. In the first one, q is negative for heat is leaving the system. In the second one, q is positive for heat is being supplied to the system.

Rebecca Doan 2L
Posts: 51
Joined: Thu Jul 27, 2017 3:01 am

Re: 9.3

when heat is exiting the system, heat is being lost so it is negative. When additional heat is entering a system, heat is being added, hence the positive sign.

Sophia Kim 1C
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 1 time

Re: 9.3

In the beginning the energy is negative because heat is leaving the system (making it negative) but when heat is added it to the system then it is positive

Patricia Macalalag 2E
Posts: 53
Joined: Sat Jul 22, 2017 3:00 am

Re: 9.3

The signs dictate the flow of energy

Meredith Steinberg 2E
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am

Re: 9.3

When heat is leaving a system, it's energy sign is negative. When it is entering a system, its energy sign is positive. This can also be applied when you're doing problem 9.5 when heat is being transferred from one reservoir to another.