Glass is Called Super Cooled Liquid. Give Reason: Super Cooling (For CBSE, ICSE, IAS, NET, NRA 2022)

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Title: Glass is Called Super Cooled Liquid. Give Reason

Super Cooling

  • Super cooling is the process of chilling a liquid below its freezing point, without it becoming solid.
  • A liquid below its freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form.
  • Though, lacking any such nucleus, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs.
  • The homogeneous nucleation can occur above the glass transition where the system is an amorphous - that is, non-crystalline-solid.
  • Super cooling, a state where liquids don՚t solidify even below their normal freezing point, still puzzles scientists today.
  • A good example of this phenomenon is found everyday in meteorology: clouds in high altitude are an accumulation of super cooled droplets of water below their freezing point.

Is Glass is Called Super Cooled Liquid?

  • Glass, however, is actually neither a liquid — super cooled or otherwise — nor a solid.
  • Glass is called super cooled liquid because glass is an amorphous solid. Amorphous solids have the tendency to flow but, slowly.
  • Ice dose not form a crystalline solid structure as particles in solids do not move but here it moves. Hence, it is called a super cooled liquid.
  • It is an amorphous solid — a state somewhere between those two states of matter.
  • And yet glass՚s liquid like properties are not enough to explain the thicker-bottomed windows, because glass atoms move too slowly for changes to be visible.
  • Glass is basically an amorphous solid. It does not form a crystalline structure. So, the constituent particles of the glass can move.
  • In regular solids, there is no movement of constituent particles under normal conditions.
  • Because of this fluidity property, glass is called as super cooled liquid. Glass can be considered as a liquid of extremely high viscosity.
  • Evidence of the fact can be seen in the windows getting thicker at bottom over a period of time.