Talk:Coefficient of thermal expansion

message: This article is full of incorrect physics. 
For example the concept of the linear coefficient of expansion belongs in the realm of 
classical physics. There is no simple explanation on an atomic level. One needs to know about 
crystal structures, amorphous materials, quasi-crystals, etc. My suggestion is to get rid of the 
explanation and just refer to the observed effect in classical physics. Another example is the reference
to freezing water -> ice. The is a phase change effect and is explained by molecular arrangement as water beings to 
form a crystal structure. It is specific to a subset of materials and alloys, thus there is no general rule for a phase change.
Also there is no need to bring partial derivatives into this discussion. The average reader will not understand
it. Please reformulate the expressions without the use of calculus. For example
   L(T) - L(To) = L(To)*( a )*( T - To)    
and this only applies over a finite temperatue range, since there are non-linear second order effects. Wiseoldowl 16:01, 28 October 2007 (UTC)
replies: text: I have tried to rewrite the article taking into account the above comments. I have tried to limit the amount of calculus, or at least keep it separate from the main explanatory sections. Ultimately, the coefficient of thermal expansion cannot be understood without a rudimentary understanding of the derivative. Much of the previous article was thrashing around due to an incomplete or improper understanding of this concept. Hopefully those who are not familiar with the limiting process and derivatives will be able to make some sense of the article and those who are can find it useful as well. Its not perfect, but its a start. PAR (talk) 19:32, 26 November 2009 (UTC)
thread_title:  Please have someone qualified write this article 

message: We need to find out the names of the different versions of the coefficient. The final authority is IUPAC according to Wikipedia. PAR 22:56, 20 December 2005 (UTC)
thread_title:  The template 

message: IT WOULD BE NICE TO HAVE A DIFF IN TEMP AND MULTIPLY THIS BY VOLUME TO GT THE VOLUMETRIC EXPANSION OF THE FLUID
Also, some temperature dependence would be nice, i.e. how does the CTE typically change as a function of temperature?  How constant is it over a wide range of T?
Walter Spieksma 15:48, 19 February 2007 (UTC)
thread_title:  It would be nice 

message: The first two senctences try to describe why there is a dimensional change with temperature change. They say 
"During heat transfer, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bond"
I find this as a hand waving explanation. I think that the explanation I offer below is a far superior, but I find myself bad at incorporating it into the article. Here is the explanation:
If a material is heated or cool, then energy has been imparted to the material proportional to its heat capacity. So, if you heat a particle it becomes more energetic. Now energy is related to velocity through E=1/2 m v2. This means that particles are now moving faster. In particular the atoms are moving faster. 
First, examine a solid; all atoms in solid form vibrate, and they do so at approximately 1013 Hz. When more energy is imparted to them they change their velocity, but not their frequency. This means the amplitude of their vibrations is larger. Hence their atomic spacing is larger.
Now if we apply the logic to the fluid phases (i.e. gases and liquids), we find that the atoms or molecules are actually traveling faster. So for molecules in air, the time of their mean free path is now shorter, or in other words, they have more collisions for a give time. Collisions can be with other gas molecules or with another phase (such as the walls of a container). Now the number, frequency, and energy of those collisions determines the pressure. As we no, the pressure is related to the volume through the the natural gas law. The same hold true for liquids, but instead of think of linear motion, rotational motions become more prominent.
Can someone add that explaination in a more eloquent form?
Walter Spieksma 15:48, 19 February 2007 (UTC)
thread_title:  Improving the phenomenological explanation 

message: There are two beta, one for the Compressibility, and one for the volumetric thermal expansion coefficient. This can lead to confusion. —The preceding unsigned comment was added by 195.68.31.231 (talk) 08:54, 7 March 2007 (UTC)
thread_title:  Confusion 

message: I have come across different sources that give different values for the coeffecient of thermal expansion of steel(just steel only). Some state it as 12.0, some 13.0, while this article states it at 11.1. So am I right to say that it is variable due to the different compositions of steel(since it is a mixture)? Please correct me if i'm wrong. Thanks AquaDTRS (talk) 15:11, 1 February 2008 (UTC)
replies: text: There are many kinds of steel. 155.212.242.34 (talk) 14:39, 15 April 2008 (UTC)
thread_title:  coeffecient of thermal expansion of steel 

message: I've seen materials listed with two alpha values, α1, and α2 for ASTM-E831 CTE values. What do these mean? 155.212.242.34 (talk) 14:41, 15 April 2008 (UTC)
thread_title:  &alpha;<sub>1</sub>, &alpha;<sub>2</sub> 

message: The article states "For exactly isotropic materials, the area thermal expansion coefficient is 2/3 of the volumetric coefficient.". Now, i'm pretty sure that's wrong, i believe the right figure is that the area thermal expension coefficient is one third the volumetric coefficient. Larryisgood (talk) 17:12, 2 May 2010 (UTC)
thread_title:  Volumetric expansion coefficient