Register to reply 
Relationship Between Density and Specific Heat 
Share this thread: 
#1
Jul2404, 05:29 AM

P: 9

I am currently studying thermochemistry and specific heat capacity has been discussed. From observing a list in order of specific heat from highest to lowest and then comparing to a list of densities, it seems to me that the denser a substance is, the lower the specific heat. Is this true and if so is there an exact relationship?



#2
Jul2404, 01:22 PM

Sci Advisor
HW Helper
PF Gold
P: 1,387

Generally, sorta true. Specific relationship? No. What you've tripped over is "equipartition" of energy of a system among the degrees of freedom of the system. Translation: As far as chemists are concerned, heat capacities, or specific heats, can be interpreted as sums of translational, rotational, and vibrational degrees of freedom of molecules; translational and rotational degrees each contribute kT/2 (or, RT/2), and vibrational degrees kT to the total heat capacity. Notice, no mention of mass  that means, roughly, that the heat capacity per mole of He is the same as that for Rn  per unit mass, He is higher. Equipartion is approximate  the vibrational degrees of freedom are not commonly fully excited, and, strictly speaking, you also have to include electronic states, nuclear states, and so on, but at temperatures at which molecules are stable (low energy excited states), you can pretty much ignore everything beyond translation, rotation, and vibration.



#3
Jul2404, 05:43 PM

P: 9

Thankyou for your reply Bystander and your explanation.



Register to reply 
Related Discussions  
Quantity of Heat/Specific Heat Water+Iron  Introductory Physics Homework  3  
Specific Heat and Phase Change/Latent Heat Problems PLEASE HELP  Introductory Physics Homework  5  
Specific heat and latent heat of fusion  Introductory Physics Homework  2  
Specific heat, latent heat, and temp  Introductory Physics Homework  3  
Specific heat capacity and latent heat of fusion  Introductory Physics Homework  4 