# How much heat energy in molten glass?

## Main Question or Discussion Point

How much heat energy is in a cubic meter of molten glass?

I would like to know how much energy would be lost if a cubic meter of glass would be allowed to cool, instead of turning the energy into something else.

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Khashishi
CWatters
Homework Helper
Gold Member
Does glass have a latent heat of fusion/melting? Just wondering.

Doug Huffman
Gold Member
Hmm, I seem to recall glass characterized as a very viscous amorphous liquid, thus no phase change on solidification.

Some people claim that glass is actually a supercooled liquid because there is no first order phase transition as it cools. In fact, there is a second order transition between the supercooled liquid state and the glass state, so a distinction can still be drawn. The transition is not as dramatic as the phase change that takes you from liquid to crystalline solids. There is no discontinuous change of density and no latent heat of fusion. The transition can be detected as a marked change in the thermal expansivity and heat capacity of the material. [my emphasis]

http://math.ucr.edu/home/baez/physics/General/Glass/glass.html

Last edited:
Staff Emeritus
2019 Award
Does glass have a latent heat of fusion/melting?
It does not. (But the "glass is a liquid" meme is an oversimplification designed more to produce a 'wow' than actual enlightenment)

sophiecentaur
Gold Member
It does not. (But the "glass is a liquid" meme is an oversimplification designed more to produce a 'wow' than actual enlightenment)
Also, there is a belief that the glass in old windows is thicker at the bottom than at the top because it has 'flowed downwards'. I think the reason is not to do with flowing but because the glass was always put in that way for strength.

Doug Huffman
Gold Member
All that is made clear in John Baez' article, the 'simplification' (of one only order phase transition) and mass orientation ("The sheets were thicker towards the edge of the disc and were usually installed with the heavier side at the bottom.").

But for strength?

sophiecentaur