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silica (silicon dioxide)

SiO{TAG(tag=>sub)}2{TAG} An abundant material on Earth, being the major constituent of sand. It is a white solid, with a high melting point (1710 Â°C) due to the structure of the solid, which is a giant covalent lattice with four Si-O covalent bonds arranged tetrahedrally (see the diagram). It forms three polymorphs: quartz, tridymite and cristobalite (all of which can exist in both low- and high-temperature forms). At high temperatures, silicates can be formed by fusion with other substances, as in the formation of slag in a blast furnace. When fused with limestone (CaCO{TAG(tag=>sub)}3{TAG}) and sodium carbonate (Na{TAG(tag=>sub)}2{TAG}CO{TAG(tag=>sub)}3{TAG}) at around 1500 Â°C and then cooled, a glass is formed.

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silanes		silica gel

Other Terms : electron | Jacob-Monod theory | Wien's (displacement) law

silica (silicon dioxide)

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silanes

silica gel