State Properties

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Jamie Huang 1L
Posts: 20
Joined: Fri Jul 15, 2016 3:00 am

State Properties

Postby Jamie Huang 1L » Wed Jan 11, 2017 10:05 pm

Why is heat not a state property, but enthalpy is considered a state property as it consists of heat?

Angela To 2B
Posts: 20
Joined: Wed Sep 21, 2016 2:55 pm

Re: State Properties

Postby Angela To 2B » Wed Jan 11, 2017 10:28 pm

Enthalpy is considered a state function because it is NOT path dependent. Enthalpy is defined as delta H which is the change in H (which we can refer to as H final - H initial)! Therefore it's a state function because we care about the final and initial (since delta H is the difference in H), rather than the path it took! Heat isn't a state property because it's a form of energy in transit. You can kind of think of it as work if that makes more sense. work is also a form of energy in transit. They occur when there's a change in the system, but not at the initial or final state. Meaning they ARE path dependent, and therefore aren't state functions/properties! I hope this helps! :)

stephanieyang_3F
Posts: 62
Joined: Wed Sep 21, 2016 2:55 pm

Re: State Properties

Postby stephanieyang_3F » Thu Jan 12, 2017 4:24 pm

Enthalpy is the amount of heat released or absorbed at a constant pressure whereas heat is one way that energy can be transferred between a system and its surroundings as a result of a temperature difference. Like Angela mentioned, heat is a path dependent function while enthalpy is a state function. It's almost like displacement and distance. You can put in a lot more energy depending on the steps you take to achieve the final state, but all enthalpy cares about is the difference between an initial state and final state.


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