State functions

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Briana Yik 1H
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

State functions

Postby Briana Yik 1H » Thu Jan 24, 2019 11:44 pm

Can someone explain why heat is not a state function? Is it not interchangeable with temperature? Thank you

Sydney To 1D
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

Re: State functions

Postby Sydney To 1D » Thu Jan 24, 2019 11:49 pm

A state function depends only on the current state of the system, any change inits value is independent of how the change in state was brought about. Heat is not a state function because the energy transferred as heat during a change in the state of system depends on how the change is brought about. There are various ways of adding and removing heat from a system to raise and reduce the temperature, respectively.

IsabelLight2H
Posts: 34
Joined: Wed Oct 03, 2018 12:15 am

Re: State functions

Postby IsabelLight2H » Fri Jan 25, 2019 12:00 am

But doesn't only the final heat value matter? Wouldn't that make it a state function?

Eva Guillory 2E
Posts: 44
Joined: Fri Sep 28, 2018 12:22 am

Re: State functions

Postby Eva Guillory 2E » Fri Jan 25, 2019 1:53 am

According to http://chemed.chem.purdue.edu/genchem/t ... 5/work.php:

"Heat and work are not state functions. Work can't be a state function because it is proportional to the distance an object is moved, which depends on the path used to go from the initial to the final state. If work isn't a state function, then heat can't be a state function either. According to the first law of thermodynamics, the change in the internal energy of a system is equal to the sum of the heat and the work transferred between the system and its surroundings."

Eva Guillory 2E
Posts: 44
Joined: Fri Sep 28, 2018 12:22 am

Re: State functions

Postby Eva Guillory 2E » Fri Jan 25, 2019 1:57 am

In addition, here is an article about the difference between heat and temperature, and why they're not interchangeable:
https://www.khanacademy.org/science/che ... sal/a/heat

In addition, http://www.physicstutorials.org/home/he ... emperature highlights some defining differences:

1) Heat is a type of energy, but temperature is not energy.

2) Heat depends on mass of the substance, however; temperature does not depend on the quantity of matter. For example, temperature of one glass of boiling water and one teapot of boiling water are equal to each other; on the contrary they have different heat since they have different masses.

3) You can measure temperature directly with a device called thermometer but heat cannot be measured with a device directly. You should know the mass, temperature and specific heat capacity of that matter.

4) If you give heat to a matter, you increase its temperature or change its phase.


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