Question

Give the reasons for following.
Glasses from ancient monuments appear milky.

Answer 1

Hint: We know that solid is a state of matter. The formation of solids takes place due to stronger force of attraction between atoms and molecules. The solids are classified in two kinds, amorphous and crystalline. Glass is an example of amorphous solid.

Complete step by step answer:
Let’s discuss the types of solid in detail. We know that there are two sets of solids namely amorphous and crystalline.
Amorphous solid is the one in which arrangements of constituent particles are not in a regular fashion, such as rubber and glass. Amorphous solids are also known as supercooled liquid or pseudo-solid. They are intermediate between solids and liquids. Amorphous solid also possesses the tendency to flow like that of liquid. However they flow in a very slow manner and this is the reason they are called pseudo solids or supercooled liquids.
Let’s discuss crystalline solids in detail. They are the solid in which there is arrangement of particles such as ions, atoms or molecules in a definite geometric pattern within the solid. Some examples of this type of solid are sodium chlorine (NaCl), potassium nitrate $\left( {{\rm{KN}}{{\rm{O}}_{\rm{3}}}} \right)$ etc.
Now, come to the question. Here, we are asked to give the reason for the milky appearance of ancient glass monuments. We know that glass is an amorphous solid and by alternate heating and cooling, it can be converted to crystalline forms. Glasses of ancient monuments undergo heating due to the exposure of sun (day time) and cooling at night and thus converted to partly crystalline form. This results in the milky appearance.

Note: We have observed many times that the glass panes fixed to windows or doors of old buildings become slightly thicker at the bottom than at the top. This phenomenon occurs due to the amorphous nature of glass. Due to its tendency to flow, it flows very slowly and makes the bottom of the window pane slightly thicker than the original.