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Structure of quartz (crystalline) and quartz glass (amorphous)

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Quartz is a form of SiO2 (silica). It has tetrahedral SiO4 units which are orderly arranged in crystalline quartz as shown.  In this arrangement, SiO4 tetrahedra are connected to one another such that oxygen atom of each SiO4 tetrahedral is shared with another atom.  When SiO2 is melted and the  melt is cooled, it forms quartz glass which is amorphous. In this state,  The  SiO4 units are randomly joined. Thus, in quartz (crystalline), SiO4 units are orderly arranged while in quartz glass (amorphous), the SiO4 units  are randomly arranged. While the two structures are almost identical, yet  in case of amorphous quartz glass there is no long range order.  The structure  of amorphous solids is similar to that of liquids.
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What is is solid state

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As we look around, most of things we see are solid substances rather than  liquids and gases.   The solids are the substances which have definite shape. In terms of kinetic molecular model, solids have regular order of their constituent particles (atoms, molecules or ions). These particles are held together by fairly strong forces, therefore, they are present at fixed positions. The properties of the solids not only depend upon the nature of the constituents but also on their arrangements and the types of forces which hold the constituent particles together in a tightly packed arrangement. The solids are rigid and maintain their own shape when subjected to outside force. On the other hand, liquids and gases change their shapes in response to outside forces. Therefore, liquids and gases are called fluids because of their ability to flow. The fluidity of liquids and gases is due to the fact that their constituent particles are free to move about. On the other ...
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