GLASS
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GLASS
   Glass is an inorganic super cooled liquid. It has no definite melting point. It has very high viscosity which    prevents its crystallization. Generally glass are the silicates of sodium and calcium.
FORMATION OF GLASS
   Glasses are formed by allowing molten silicates to cool.
TYPES OF GLASS
ORDINARY WINDOW GLASS (SODA GLASS)
   Preparation:
   It is prepared by heating a mixture of silica (SiO2), Na2CO3 and CaCO3 in a furnace.
Na2CO3 + SiO2 è Na2SiO3 + CO2
CaCO3 + SiO2 è CaSiO
3 + CO2
   Properties:
   It is not a very expensive kind of glass.
   It is easy to work .
   It breaks and get scratched easily.
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   Uses :
   Bottles, windows,flat glass sheet.
BOROSILICATE
OR
PYREX GLASS
   Preparation:
   It is prepared from silica, Boron oxide (B2O3),Aluminum oxide (Al2O3) and sodium oxide (Na2O).
   Properties:
   It has high softening temperature. It bears high temperature.
   Uses :
   Laboratory wares such as beakers, test tube, flask etc.
CRYSTAL GLASS
   Preparation:
   It is prepared by silica, lead oxide (PbO) potassium carbonate (K2CO3) and CaCO3.
   Properties:
   It is heavy glass. It is very expensive.
   Uses :
   In decorative glass show piece.
COLOURED GLASS
   Preparation:
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   It is prepared by mixing different chemical compound in molten glass. These compound give a particular    colour to glass.
   e.g:
   red colour :Cu2O and AuCl3
   Blue : CuO
   Green :Cr2O3
WATER GLASS
   Na2SiO3 is commonly known as water glass.
   Preparation:
   It is prepared by heating sodium carbonate with silica.
Na2CO3 + SiO2 è Na2SiO3 + CO2
   Uses :
   It is used in the manufacture of fire proofing material.
SILICA GEL
   When an acid is added to a solution of water glass, it turns into a jelly like substance known as Gel    (SiO2.H2O) on heating the Gel dehydrates and forms a hard porous material which is known silica Gel.    It is a good moisture absorbent and is used in medicine packing to absorb moisture.
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