Difference between enthelphy and heat?

  • Context: Undergrad 
  • Thread starter Thread starter asdf1
  • Start date Start date
  • Tags Tags
    Difference Heat
Click For Summary

Discussion Overview

The discussion centers on the distinction between enthalpy and heat within the context of thermodynamics, exploring theoretical definitions and practical applications. Participants examine how these concepts relate to different thermodynamic processes.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant presents the equation for enthalpy as \( H = U + PV \) and questions the apparent similarity to the equation for heat, seeking clarification.
  • Another participant suggests that the context of the situation is crucial, explaining that in certain processes, such as flow through a pipe, the heat added or removed corresponds to the change in enthalpy.
  • A different viewpoint is introduced, stating that enthalpy is a property of a substance while heat is described as a transport phenomenon, implying that heat does not constitute a property in the same sense.
  • One participant notes that under constant pressure with only expansion work, the enthalpy change equates to the heat transfer, referred to as \( q_p \).

Areas of Agreement / Disagreement

Participants express differing views on the nature of enthalpy and heat, with some emphasizing the contextual application of these concepts while others focus on their theoretical definitions. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants reference specific thermodynamic scenarios that may influence the relationship between enthalpy and heat, indicating that assumptions about the system's conditions (e.g., constant pressure) are significant but not fully explored.

asdf1
Messages
734
Reaction score
0
in my thermodynamics textbook, enthalphy=U+PV
and (delta)heat=(delta)U+(delta)PV
those 2 look the same...
can anybody explain the difference?
@@
 
Science news on Phys.org
Hi asdf1. Take a look at your book again, I think you've taken it out of context. For example, flow through a pipe where heat is added or removed between two points in the pipe is a process in which the heat added/removed is equal to the enthalpy change in the fluid. On the other hand, for the situation where heat is added to a sealed container (ex: a pressurized tank), the amount of heat added or removed is equal to the change in the fluid's internal energy.
 
I was taught that enthalpy was a property of a substance. Heat is a transport phenomenon only (i.e. transfer of energy) and that there is no such property as heat.
 
at constant pressure with only expansion work the enthalpy of the substance does equal to the heat pertaining to the situation, that is [tex]q_p[/tex]
 
thanks! :)
 

Similar threads

  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 22 ·
Replies
22
Views
4K
  • · Replies 28 ·
Replies
28
Views
4K