Standard Temperature Notation for Phase Change

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Discussion Overview

The discussion revolves around the notation used to specify temperatures at phase changes, particularly in the context of water transitioning between liquid and solid states. Participants explore whether there is a standard shorthand for indicating the state of a substance at a given temperature, especially when considering latent heat and phase changes.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions if there is a standard way to denote temperature at a phase change, suggesting that the lack of clarity can lead to multiple interpretations of energy calculations.
  • Another participant interprets temperature statements as implying no phase change unless specified otherwise, advocating for explicit descriptions of the state of the substance.
  • A different participant emphasizes the need for detailed specifications, including the state of the substance and pressure, to avoid ambiguity in questions related to phase changes.
  • One participant notes the absence of a shorthand notation for differentiating between the hot and cold sides of a phase change, despite familiarity with terms like STP (Standard Temperature and Pressure).
  • Another participant mentions historical shorthand notations used in water and steam engineering, such as "32 deg F liquidus" and "32 deg F solidus," which include subscripts to indicate the state of the substance.

Areas of Agreement / Disagreement

Participants generally agree that clarity in specifying the state of a substance is crucial, but there is no consensus on a standardized shorthand notation for indicating the temperature at phase changes.

Contextual Notes

Participants highlight the importance of including additional context, such as pressure and specific states, to ensure unambiguous communication in thermodynamic discussions.

CWatters
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°Thought just occurred to me.. Is there a standard way of referring to temperature either of a phase change?

For example if I write..

"1kg of water is cooled from 20°C to 0°C, how much energy was removed?"

...then potentially two answers might be considered correct depending if you include the latent heat or not. In many cases it's obvious because a problem statement might say.. .

"water at 0C is heated...
or
"Ice at 0C is heated...

and "water" or "ice" implies which side of the phase change you are starting from but is there a standard or shorthand way to write (for example) "0°C" that differentiates between one side of the phase change vs the other?
 
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I would interpret the statement as if there was no phase change. If there was a phase change I would say "cooled to 0 °C and frozen".
 
This is an example of a situation in which you just have to specify the situation in more detail than you may think necessary. You would need to include the state of the substance and also, even, the pressure for the experiment - if you wanted it to be an unambiguous question. Orodruin's interpretation was a fair one, in the absence of more information. In the case of water / water vapour there is such a wide possible range of conditions that, unless the ambient pressure is stated, we could be dealing with either or both states, over a huge range of temperatures. Even down to the time needed to boil and egg :smile:.
 
I guess the answer is no then.

I understand phase diagrams and I'm familiar with short hand such as STP for Standard Temperature and Pressure. Was just curious why there seemed to be no short hand for differentiating between the hot or cold side of a phase change.
 
Old books on water and steam engineering do sometimes use a convenient shorthand notation :

Like this : 32 deg F liquidus and 32 deg F solidus .

Usually actually written with subscripts liq or sol behind the F .

Other ones for steam in various conditions including ones like 250 F subscript 0.8 ( where 0.8 is the dryness fraction) .
 
Thanks for that.
 

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