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Temperature notation

  1. Sep 3, 2015 #1

    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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  3. Sep 3, 2015 #2

    Orodruin

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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".
     
  4. Sep 3, 2015 #3

    sophiecentaur

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    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:.
     
  5. Sep 4, 2015 #4

    CWatters

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    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.
     
  6. Sep 4, 2015 #5

    Nidum

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    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) .
     
  7. Sep 5, 2015 #6

    CWatters

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    Thanks for that.
     
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