Is glass a solid or a liquid?

Is glass a solid or a liquid? When you see the title, you may definitely say that it is a solid, but strictly speaking, glass is not a solid. It is a semi-solid and semi fluid state with a relatively slow flow rate.

Many old churches in the West that have been used for over a century have window glass that is thin on the top and thick on the bottom. This means that when a flat glass is vertically placed for a hundred years, it becomes thinner on the top and thicker on the bottom, exhibiting liquid properties. This is similar to the situation where soap film becomes thin on the top and thick on the bottom due to gravity. In fact, many science popularization books and TV science popularization propaganda videos have talked about this popular science knowledge, which is not a new thing.

Glass is not entirely solid

Glass is neither crystalline nor amorphous, nor polycrystalline, nor mixed. The theoretical name is glassy state. The characteristic of glassy state at room temperature is short-range ordering, which means that atoms are arranged in an ordered manner within a range of several or dozens of atoms, exhibiting crystal characteristics. Long range disorder, that is, after increasing the number of atoms, becomes a disordered arrangement state, with a degree of disorder similar to that of a liquid. Macroscopically, glass is also a solid substance. Glass is such a substance. The reason for the structure of glass is that the viscosity of glass changes too quickly with temperature, and the crystallization rate is too slow. When the temperature drops and crystallization begins, the viscosity has already become very high, restricting the movement of atoms and causing this result. So, the glassy state is similar to a solid liquid, and the atoms in the substance are always in the process of crystallization.

Therefore, although the atomic positions in glass appear fixed, there are still forces between the atoms that promote their tendency to rearrange. It is not a stable state, which is different from the atomic state in paraffin. So, neither is it a crystal. At room temperature, paraffin is completely solid, while glass can be seen as a highly viscous liquid.

Revealing the Mystery of Non Solid Glass

In the experiment, researchers used larger colloidal particles to simulate atoms and observed them under a high-power microscope in order to observe the true motion of microscopic atoms. It was found that the gel formed by these particles could not form crystals because it formed an icosahedral structure, which was consistent with the prediction made by Charles Frank of Bristol University in the 1950s. This structure explains why glass is a "glass" rather than a liquid or solid.

This research is a significant breakthrough in understanding metastable materials, which will make it possible to further develop new materials such as metallic glasses. In addition, if the metal can be manipulated to form a glass like internal structure during cooling, it may greatly reduce metal defects.

Some materials form crystals when cooled, and their atoms are arranged in a highly regular pattern called a "lattice". However, when glass is cooled, atoms are packed together and arranged almost randomly, hindering the formation of a regular lattice.