Is Glass a Liquid or Solid?

There's an ongoing debate on whether glass is supercooled liquid or solid. However, it is reportedly neither of the two.

Is Glass a Liquid?

Sometimes, the glass in cathedrals in medieval Europe seems strange. Some panes have bottoms that are thicker than tops.

The glass, which appeared to be solid, looked like it melted, which prompted some to speculate that glass is a liquid. However, since glass is a hard substance, some were convinced it is a supercooled liquid.

In reality, glass is neither a liquid (supercooled or not) nor a solid. It is an amorphous solid that can exist in any of those two states. The thicker-bottomed windows cannot be explained only by the liquid-like characteristics of glass since glass atoms move too slowly for any changes to be evident.

Structures made of solids are very well-ordered. According to Mark Ediger, a chemical professor at the University of Wisconsin, Madison, these crystals include salt and sugar crystals, with millions of atoms lined up in a row. He observed that glasses and liquids don't have the inversion. Glasses do not achieve the rigid order of crystals while being more structured than liquids. He added that amorphous signifies that it lacks the long-range order. Solid materials tend to keep their shape.

When silica-containing materials make glass, they are quickly chilled from their liquid form but do not solidify when their temperature falls below their melting point. At this point, they are in a condition known as a supercooled liquid, which is between a liquid and a glass.

The substance is cooled below the glass-transition temperature to transform into an amorphous solid. The substance is now a glass since the atoms' molecular mobility has slowed to almost a standstill past this point. Because it did not freeze, this new structure is less structured than a crystal but more organized than a liquid. For practical reasons, like holding a drink, Ediger claims that glass is similar to a solid, albeit a disorganized one.

These disordered solids can flow, albeit extremely slowly, like liquids. According to Ediger, the molecules that makeup glass gradually rearrange themselves to form a more stable, crystal-like shape over a lengthy period of time.

The more a glass shifts as it approaches its glass-transition temperature, the farther it is from that temperature, the slower its molecules move, and the more solid it appears to be.

What Is an Amorphous Solid?

An amorphous solid is any noncrystalline substance whose atoms and molecules lack a clearly defined lattice pattern. These solids include gel, glass, and plastic.

Solids can be divided into two primary categories: crystalline and amorphous. Their atomic-scale structure is what sets them apart from one another.

Long-range order, also known as translational periodicity, is a characteristic of atomic locations in crystals. These positions recur in space in a regular pattern. There is no translational periodicity in an amorphous solid. No long-range order exists. However, unlike in the gas, the atoms are not dispersed randomly in space.

Other terminology in use include vitreous solid, noncrystalline solid, amorphous solid, and glass. Glass and vitreous solid have historically been used to describe an amorphous solid produced by rapidly cooling (quenching) a melt. Amorphous solids and noncrystalline solids are more broad terminology.

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