Temperature Vs. Heat

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Stephanie Manzo 1H
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Temperature Vs. Heat

Postby Stephanie Manzo 1H » Mon Jan 04, 2016 11:22 pm

Why is temperature a state property and not heat?

704578485
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Re: Temperature Vs. Heat

Postby 704578485 » Tue Jan 05, 2016 10:55 am

State properties are one in which change in the variable can simply be calculated by doing the final value subtracted by the initial value. For temperature this works because let's say you start at 45 degrees celcius and then go down to 20 degrees celcius and then up to 60 degrees celcius, the change in temperature will be 15 degrees celcius. The change in heat (unless pressure is constant) is not a state function because delta(q) is dependent on the path it takes. Although temperature and heat are very closely related you have to look at heat as energy just as work is energy. If you and your friend go to the grocery store, although you two ended up in the same place, if you walked and she drove, your energy used would be greater.

Chem_Mod
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Re: Temperature Vs. Heat

Postby Chem_Mod » Wed Jan 06, 2016 12:22 am

Temperature is a measure of the average velocity of molecules and it has units of Celsius or Kelvin. It is a state function and only depends on the current motion of molecules. Heat is a transfer of energy and has units of Joules. It represents the path taken to go from one state to another, so it is not a state function.

Being careful with wording can help to clear up the difference! While a certain state "has a temperature", you cannot say that it "has heat". Heat is only meaningful in the context of a transfer.

Sabina Fridman 1D
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Re: Temperature Vs. Heat

Postby Sabina Fridman 1D » Thu Jan 07, 2016 6:01 pm

on this same topic, we always know that heat is either given off/absorbed if there is a difference between final and initial temperatures, right?

MichelleVu2H
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Re: Temperature Vs. Heat

Postby MichelleVu2H » Thu Jan 07, 2016 6:14 pm

I would assume so. The loss or addition of heat into a system would cause a change in temperature or that the reaction gave off energy in the form of heat.

Chem_Mod
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Re: Temperature Vs. Heat

Postby Chem_Mod » Fri Jan 08, 2016 1:24 am

The temperature can be changed by having only work and no heat transfer. This is an adiabatic process. In U=q+w, U is the quantity that is related to temperature. So even if q=0, the work part can change the temperature.


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