How Can Water Heat Up with Negative Heat Transfer?

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Discussion Overview

The discussion revolves around the concept of how liquid water can experience a temperature increase from 25°C to 30°C under conditions where the heat transfer (q) is negative. Participants explore the implications of specific heat, internal energy, and the relationship between heat transfer and work input in this context.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how q can be negative while the temperature change is positive, suggesting a potential connection to specific heat and its dependence on temperature.
  • Another participant expresses uncertainty about the nature of specific heat, questioning whether it is indeed a constant.
  • A different viewpoint is introduced, stating that negative heat flux does not imply that work input is also negative, indicating that work can raise the temperature of a fluid.
  • One participant references an energy equation, suggesting a relationship between heat input, work output, and changes in internal energy.
  • A participant acknowledges the suggestions provided and seeks further input on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between heat transfer, specific heat, and work input, indicating that multiple competing perspectives remain without a consensus.

Contextual Notes

Participants do not fully resolve the implications of specific heat variability or the conditions under which q can be negative, leaving some assumptions and definitions unclear.

notawretcheddrunk
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perhaps I'll get more replies here

"explain how liquid water can go from 25C/1 atm to 30C/1 atm in a process for which q<0"

I was thinking perhaps that since , [tex]q=mc_p \Delta T[/tex] how can q be negative when the temperature change is positive? , maybe it has something to do with the specific heat, however the only other factor which effects cp is temperature right? Well since the tempreature change is already given, I'm not quite sure how one can say that it is due to cp, me thinks it shouldn't be. unless the average change in cp is negative for an increase in temperature.

I guess it has to do with internal energy, but how is it that q is not always dependent on temperature then when we are given the q equation? How can we explain the situation in terms of the heat equation (above).
 
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I have no idea. I thought specific heat was a constant??

Is this a legit question?
 
Just because heat flux is zero or negative, doesn't mean work input is zero or negative. If you put work into a fluid, you raise the temperature.
 
I was reading the question and I couldn't see Q_Goest's response, but I was thinking the same thing. Energy equation Qin - Wout = U2-U1
 
ahh that sounds plausible, thanks for the suggestions so far, any other suggestions?
 

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