How does sand turn into something transparent like glass?
In: Chemistry
So there are two different criteria which determine whether a material is transparent.
The first is related to the interaction between light and the electrons in the material. Generally speaking a material can only absorb a photon if its energy is immediately used to promote an electron to a higher energy state. If a photon hits something but its energy is lower than what is required for electronic transitions it won’t be absorbed and will simply pass through, making the material transparent to that wavelength of light.
The second criterion is that the material needs to be highly homogeneous. Ice is transparent, but snow isn’t despite being just a lot of small ice crystals. This is because some light is reflected off each face of the ice crystals, and given that there’s so many of them what eventually happens is that all light is reflected or scattered away resulting in an opaque appearance.
Sand is made primarily of quartz, which is transparent in its single-crystal form. However, as each grain of sand is made up of lots of small quartz crystals it becomes opaque. When you melt it to produce glass, the crystals dissolve and the material solidifies as a homogeneous, disordered structure where there’s no crystals to scatter light away.
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