Expert: Scotto - 7/22/2009

Question
What exactly determines it? and why does it differ between the elements , is it e physical attribute or a chemical one ?

also why doesn't some elements like carbon get thermally expanded?

Answer
Linear Thermal Expansion is based on the material and the change in termperature.  If the temperature gets really high, it can also cause chemical reactions.  All that I can say about it being different is that's the way they've measured it.  That's along the same lines as asking why various chemiclas boil at different temperatures.

I found 3 articles that might interest you.

1) Title: Glossary of fuel cell terms - Wikipedia, the free encyclopedia

It is a physical attriabute.  If the temperature rise high enough,
then it becomes a chemical one as materials change form or a fire occurs.  Again, these properties depend on the compound.
From en.wikipedia.org/wiki/Glossary_of_fuel_cell_terms,
I found out that thermal oxidation occurs down under the areas that start with "Thermal".  The terms are alphabetical, so it is weigh down near the bottom.


2) Title: Coefficient of thermal expansion - Wikipedia, the free encyclopedia

A really good article on termal expansion is
en.wikipedia.org/wiki/Coefficient_of_thermal_expansion


3) Title of place: Thermal expansion - Wikipedia, the free encyclopedia

In en.wikipedia.org/wiki/Thermal_expansion, I found,
 "Thermal expansion generally decreases with increasing bond
  energy, which also has an effect on the hardness of solids, so,
  harder materials are more likely to have lower thermal expansion.
  In general, liquids expand slightly more than solids."

Down at the bottom, there is a section on Anisotropy, which says that in some cases, there is a structure to the material that does not let it expand or contract much at all.

Down in the section labelled, "Thermal expansion coefficients for some common materials", it list out the expansion units for various substances like Gasoline, Water, Rubber, Concrete, Steel, Iron, Glass, Diamond, Quartz (fused), Oak, and Pine.