Heat Capacity & Density: Math Relation Explored

[LeoYard]

How does heat capacity relate (mathematically) to density?
I imagine first relating entropy to density, it will depend on the molecular structure and everything, but is there a general formula ?
http://en.wikipedia.org/wiki/Volumetric_heat_capacity

I found this link, and it deals with Volumetric Heat Capacity. It is not exactly what I'm looking for.

Can one make the assumption that decrease in density leads to increase in degrees of freedom, entropy?

 

[Astronuc]

The effect may depend on the phase: solid, liquid or gas. Even in solids, metals, ceramics, organic molecules are all different.

Some relevant discussion, but not enough detail.
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/dulong.html
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html

Certainly the interatomic or intermolecular forces change with decreasing density, which would seem to introduce changes in atomic vibration and perhaps introduce modes which would otherwise not be present because of constraint. The amplitude of vibration would also change.

 

[LeoYard]

Thank you for the links. So, we can't be more specific than that. I thought of excluding solids. But, still the way substance (gas or liquid) behaves depends very much on its temperature in non-trivial ways.