Re: pinhole heat confusion

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Wed May 16 2001 - 16:31:37 PDT 

Message-Id: <l03110737b728bd92b893@[192.174.2.173]>
Date: Wed, 16 May 2001 16:31:37 -0700
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole heat confusion

>Chemists seem to talk about heat in two different ways: as a quantity
>Q and as the enthalpy H of a substance or reaction. What is the
>difference in these two ways of describing heat?
>

Heat is a flow of energy measured in Joules. (The flow is naturally from an
object at high temperature to an object at a lower temperature, although a
heat pump can use other forms of energy to move heat from cold to hot.)

Enthalpy is the heat flow that occurs in a reaction at constant pressure.

Thus they both have the same units but different definitions.

Paul D

Paul "But it is more complicated than that!" Doherty,
Senior Staff Scientist, The Exploratorium.
pauld@exploratorium.edu, www.exo.net/~pauld

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