# How much heat energy in molten glass?

Jay Lakoda
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.

Jay Lakoda
Jay Lakoda
Depends on the temperature. Here's the specific heat capacity of (some kind of) glass at 20C. It probably changes as you go up in temperature, but this should get you a rough estimate.
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/sphtt.html
Thank you =)

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

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

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Staff Emeritus
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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)

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.

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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?