Man Made Materials
Glass is a homogeneous mixture containing sodium and calcium silicate. It is non-corrosive and widely used in various fields. It is also known as super cooled liquid or pseudo solid due to its ability to flow.
Manufacture of glass:
• Raw materials: Scrap glass, sand, limestone and sodium carbonate are the raw materials used for the manufacture of glass.
• Process: Raw materials in the finely powdered form are introduced into furnace at a temperature of about 1700-1800°C, where sodium and calcium carbonate reacts with silica to form sodium and calcium silicate respectively.
Na2CO3 + SiO2 → Na2SiO3 + CO2
CaCO3 + SiO2 → CaSiO3 + CO2
The molten glass thus obtained is cast into the mould or drawn into various shapes. It is slowly cooled to provide tensile strength; this slow cooling process of glass is known as annealing. It is done, because on sudden cooling glass may be crack or bubbles amy appear on the surface of the glass..
Note: To remove air bubbles in the glass …
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