# I Heat Capacity of Solids

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1. Jan 29, 2017

### pangru

According to Einstein (or Debay) model of solids, heat capacity drops exponentially at low temperatures:

question is >> why it changes so dramatically at low temperature
that is physical explanation of this?

2. Jan 30, 2017

### BvU

Hi,
Don't understand your question -- in the sense that where you found the picture, there also is a derivation of the expression. With a link to Debye for lowest T
Or do you seek an answer like "degrees of freedom are frozen" at low T ?

3. Jan 30, 2017

### pangru

yes, something like that

at low T, heat capacity is very low >> how this could be explained?
without math

4. Jan 30, 2017

### ZapperZ

Staff Emeritus
BvU just did!

Zz.

5. Feb 4, 2017

### pangru

do you mean this? >> degrees of freedom are frozen" at low T
OK. .. and that does frozen degrees of freedom means? :D

Imagine you are Einstein, How would explain this to your grandmother? :D

6. Feb 4, 2017

### ZapperZ

Staff Emeritus
1. If my grandmother asks me that question, then she would have had some basic knowledge to know the figure she showed me in Post #1. In other words, she would have had to know what "heat capacity" is, what "Debye model" is to describe such heat capacity, the statistical derivation of it, and to know what that figure is saying. This means that she is well-equipped to comprehend the answer.

2. My grandmother was also not a lazy woman. She would have used everything at her disposal to figure out what freezing of the degree of freedom have anything to do with the specific heat curve. She was also pretty sharp to know when an answer to her question was already given and not have missed it this badly.