specific heat

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From: Karen Kalumuck (karenk@exploratorium.edu)
Date: Mon Sep 18 2000 - 10:58:35 PDT 

Date: Mon, 18 Sep 2000 10:58:35 -0700 (PDT)
Message-Id: <v01540b00b5eba46495a6@[192.174.2.182]>
From: karenk@exploratorium.edu (Karen Kalumuck)
Subject: specific heat

Hi All!

I agree that the specific heat of ammonia being higher than that of water
does not intrinsically make sense, since nitrogen is less electronegative
than oxygen and ammonia makes fewer hydrogen bonds than water.

Perhaps, and this is purely speculation, the higher specific heat is an
artifact of the way in which specific heat is determined. All materials'
specific heat is determined with the substance in liquid form (and yes,
that does include substances like salt and lead which will turn liquid at
high enough temperatures.) Pure ammonia at room temperature is a gas (the
ammonia cleaner you buy is largely water --- the ammonia in it is gaseous
as evidenced by the strong odor when you open the bottle); ammonia in
liquid form exists at about -50 degrees C (don't quote me on that exact
temperature, but it's WAY cold). There could be some sort of artifact
regarding low temperature involved, or hydrogen bonding isn't the whole
story. However, that it's a major part of the story doesn't appear to be
in dispute.

---Karen

Karen E. Kalumuck, Ph.D.
Biologist
Exploratorium Teacher Institute
3601 Lyon St.
San Francisco, CA 94123
415-561-0313
karenk@exploratorium.edu

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