State functions

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Jessica Chen 2C
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am

State functions

Postby Jessica Chen 2C » Mon Jan 27, 2020 1:37 am

Why is enthalpy a state function, but not heat? I understand how a property like distance isn't a state function, but it's harder for me to understand with heat.

Justin Quan 4I
Posts: 104
Joined: Sat Sep 14, 2019 12:17 am

Re: State functions

Postby Justin Quan 4I » Mon Jan 27, 2020 8:24 am

Firstly, a state function is a property whose value does not depend on the path taken to reach that specific value. In other words, state functions are variables that define a system. Heat is not a state function because heat is amount of thermal energy that enters or leaves the system during a process. Thus, heat is a change in energy, not an amount of contained energy in the system.

JohannaPerezH2F
Posts: 94
Joined: Wed Sep 18, 2019 12:18 am

Re: State functions

Postby JohannaPerezH2F » Mon Jan 27, 2020 8:34 am

enthalpy is a state function because it only depends on the initial and final conditions, and not on the path taken to establish these conditions

805394719
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

Re: State functions

Postby 805394719 » Mon Jan 27, 2020 10:30 am

Heat is not a state function because it does not depend on the initial and final conditions of a system. For example, enthalpy which describes the change in the heat of the system depends on the difference between the final and initial state of the system. Therefore, as long as the final and initial states remain the same, the difference between the two will always stay the same independent of the path taken to reach the final state. Heat, however, describes a quantity rather than a difference. The current heat of the system does not depend on the initial and final state of the system, it does not equal to the difference between the two. By calculating the difference between the final and initial states, we cannot get the heat of the system now. We can only get the heat of the system by either adding the change to the initial state or by measuring it directly. By definition heat is the transfer of energy that results from a difference in temperature, which is a state function.

Lauren Tanaka 1A
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

Re: State functions

Postby Lauren Tanaka 1A » Mon Jan 27, 2020 9:58 pm

Enthalpy is a state function since it depends on both the final and initial conditions of the system. Heat would not be a state function because heat is a measurement of change in energy and does not depend on the final and initial conditions of the system.

sarahsalama2E
Posts: 164
Joined: Fri Aug 30, 2019 12:16 am

Re: State functions

Postby sarahsalama2E » Mon Jan 27, 2020 10:48 pm

Examples of state functions are the following: Pressure, Density, Temperature, Volume, Enthalpy, internal energy, gibbs free energy, and entropy.


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