Glass is a special name given to those amorphous solids which are prepared by rapid cooling of the melt. They are continuous with and analogous to liquid state of that substance which has come in solid form due to very high viscosity. When you heat a glass they undergo second order phase transition at a temperature where specific heat of the glass changes suddenly and structure become flexible. This temperature is known as glass transition temperature. On further heating it crystallizes releasing extra energy and comes to minimum energy state. This temperature is known as crystallization temperature. This transition should occur in all amorphous materials but glass transition is specific to glasses. The answer given by Shikha, Anjani and Satwinder Singh are on the same lines.
Thanks, Dr. Shikha yes all the glasses are amorphous but all the amorphous are not glasses.
All amorphous materials do not exhibit GLASS TRANSITION TEMPERATURE. Those, which exhibit this characteristic are called GLASS.
Dr. Shikha has given a very interesting and perfect answer.
Glass is a special name given to those amorphous solids which are prepared by rapid cooling of the melt. They are continuous with and analogous to liquid state of that substance which has come in solid form due to very high viscosity. When you heat a glass they undergo second order phase transition at a temperature where specific heat of the glass changes suddenly and structure become flexible. This temperature is known as glass transition temperature. On further heating it crystallizes releasing extra energy and comes to minimum energy state. This temperature is known as crystallization temperature. This transition should occur in all amorphous materials but glass transition is specific to glasses. The answer given by Shikha, Anjani and Satwinder Singh are on the same lines.
Thanks Prof Ashok Kumar sir for your nice discussion, which clears basic difference between amorphous and glass.
At the signalled paper we have tried to make a distinction between the often confused concepts of amorphous and glassy states (and corresponding material substances):
Article Aspects of the non-crystalline state
I would like to add to Dr. Shika Shukla's answer. The point is to recognize that glass is a subset of amorphous solid. However, amorphous solids can be rubbery or glassy. Both are structurally similar but rubbers can undergo molecular rearrangement during the time scale of the experiment while glasses can not. As an amorphous material is cooled from the melt, solid forms first in the rubbery state existing in the range of melt temperature to the glass transition temperature and when cooling is continued below the glass transition temperature glassy solid forms (source: Schaffer, et al., McGraw -Hill, 2 edition, ISBN 0-256-24766-8, page 168, chapter 6)
Thanks Prof. Shrinivasan, really the glass is A subset of amorphous materials.
This is a very interesting question and I suggest reading the paper "Non-crystalline solids: glasses and amorphous solids" by Prabhat Gupta (link below). In this paper it becomes clear that amorphous solids and glasses are both non-crystalline materials but they are thermodynamically distinct. The difference is that glasses have short range order (SRO) that is equal to the melt, whereas this is not true for amorphous solids. However, one should pay attention because sometimes these terms are used interchangeably.
http://www.sciencedirect.com/science/article/pii/0022309395005021
Article Non-Crystalline Solids: Glasses and Amorphous Solids
From merely a physical point of view:
If vitrification or amorphization (retaining structural disorder) is affected via a thermo-kinetic processes (cooling from a melt), the resulting disordered vitreous solid is called glass. If vitrification or amorphization is affected via mechanical (millling/shock) or optical process (laser) or by ion irradiation, we will NOT call the resulting solid a glass. Thus glass is a specific sub-set of Amorphous (disordered) solids.
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