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From: gv@hou2e.UUCP (A.VANNUCCI)
Newsgroups: net.physics
Subject: Re: A question about physics and NOT metaphysics
Message-ID: <574@hou2e.UUCP>
Date: Mon, 13-May-85 18:34:28 EDT
Article-I.D.: hou2e.574
Posted: Mon May 13 18:34:28 1985
Date-Received: Tue, 14-May-85 20:47:13 EDT
References: <111@gtss.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
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In article <1397@mtx5b.UUCP> mat@mtx5b.UUCP (Mark Terribile) writes:
>I hope that a question about real things in the real world isn't out of
>place here.
>
>	Consider the specific heat of various materials.  The specific
>heat of metals is very low ... approximately one fifth to one tenth that of
>water.  Ceramics and glassy materials have specific heats that are
>approximately the specific heat of water, give or take a factor of one part
>in three.
>
>	Now it is possible to take certain metals in the molten phase and
>cool them very rapidly, as by spraying them against a rotating wheel cooled
>by liquid nitrogen.  The result is an amorphous, non-crystaline solid made
>from the metal in question: a metallic glass.
>
>	Is the specific heat of such a material more reminiscent of the
>specific heat of the metallic phase of the material, or is it reminiscent
>of the specific heat of glass?

  From the book "University Chemistry" by Bruce H. Mahan, (c) 1969 by
Addison Wesley.

"  Section 3.7

	According to the law of Dulong and Petit, the heat capacity of one
gram atom of a solid element is approximately 6.3 cal/deg.  We have seen
that the application of this rule is not limited to elements, for
experiments show that the heat capacity of many solids, elemental or
compound, is 6 cal/deg *per mole of atoms*.  Of course, there are
exceptions to this law. There are many substances whose heat capacities,
measured at room temperature, are much smaller than predicted.  These
exceptional substances are high-melting crystals that are made up of light
atoms, such as boron, carbon and berillyum. Moreover, the Dulong and Petit
law fails for all substances if the heat capacity is measured at low
temperatures.  That is, the heat capacity of a solid is not constant, but
increases with increasing temperature. At the absolute zero of temperature
the heat capacity of all substances is zero. As the temperature is raised,
the heat capacity increases, but at different rates for different 
substances. Finally, in the limit of very high temperatures, the heat
capacity of all solids is 6.3 cal/deg *per mole of atoms*.

	The key to understanding the temperature dependence of the heat
capacities of solids was supplied by Einstein in 1905....."


	Indeed, that is the work for which Einstein received the Nobel
prize.  It turns out that the departure from the Dulong and Petit law
at low temperatures is a quantum-mechanical effect and played a key
role in the development of Quantum Mechanics.

		Giovanni Vannucci
		AT&T Bell Laboratories      HOH R-207
		Holmdel, NJ 07733
		hou2e!gv