Page 1 of 1

state property

Posted: Sun Jan 21, 2018 4:11 pm
by Jessica Wakefield 1H
Can someone explain why heat is not a state property. I understand why enthalpy (qp) is a state property but want to know why heat itself (q) isn't.

Re: state property

Posted: Sun Jan 21, 2018 4:14 pm
by Harrison Wang 1H
Heat is not an intrinsic property of a system, as it only occurs when there is a temperature difference between two objects. Intrinsic properties would be like pressure or volume.

Re: state property

Posted: Sun Jan 21, 2018 4:22 pm
by Arjun Sharma 1D
So think of a car going down a hill and theres something at the bottom of the hill the car's going to hit. If the car breaks on its downhill approach to the object, it uses more heat than work in the process. If the car doesn't break and wildly goes straight into the object, it uses more work than heat. At the end of the day, the change in internal energy of the system is the same in both cases (since it is a state function), but the heat (q) and work (w) were different in the two scenarios since they are pathway dependent (which is why they're not state functions). I found this in a video and it helped me a bit, hope it was helpful to you to :)

Re: state property

Posted: Sun Jan 21, 2018 4:32 pm
by Emily Oren 3C
Heat and work are not state functions because they depend on the path taken (like distance traveled), while enthalpy is a state function because it does not depend on what happens between the initial and final states (like elevation gain). For example, if there is a reaction in which there is no change in enthalpy (because the initial and final states are the same) but there is heat transfer involved (the same amount of heat enters and leaves the system over the course of the process).