Which one among the following statements is not true for glass?

The correct answer is  Crystallinity develops on cooling of the molten mass of the glass.

Key PointsExplanation of Statements

• Sodium silicate is known as water glass
  • Sodium silicate, also called water glass or liquid glass, is a compound containing sodium oxide (Na2O) and silica (SiO2). It is known for its adhesive, fire-resistant, and antiseptic properties. Hence, statement 1 is correct.
• Glass is also called super cooled liquid
  • Glass is often referred to as a supercooled liquid because it does not crystallize upon cooling but retains a disordered structure similar to that of a liquid. This terminology highlights its amorphous nature. Hence, statement 2 is correct.
• Crystallinity develops on cooling of the molten mass of the glass
  • This statement is incorrect because glass is an amorphous solid, meaning it does not have a crystalline structure. Upon cooling, the molten glass retains a disordered arrangement of molecules rather than forming a crystalline lattice. Hence, statement 3 is incorrect.
• Coloured glasses can be made by adding different colouring materials
  • Coloured glasses are produced by adding various metallic oxides or other compounds to the glass mixture. For example, adding cobalt oxide results in blue glass, while adding chromium oxide produces green glass. Hence, statement 4 is correct.

Additional Information

• Amorphous Solid
  • An amorphous solid is a solid that lacks the long-range order characteristic of a crystalline structure. Examples include glass, gels, and many plastics.
  • The atoms in amorphous solids are arranged more randomly than in crystalline solids, resulting in different physical properties.
• Supercooled Liquid
  • A supercooled liquid is a liquid that has been cooled below its normal freezing point without solidifying. Glass is often described as a supercooled liquid because it does not form a crystalline structure when it solidifies.
  • This property gives glass its unique characteristics, such as transparency and brittleness.
• Metallic Oxides in Glass
  • Metallic oxides are used to impart color to glass. For example, adding iron oxide can produce a range of colors from green to brown, while manganese dioxide can result in purple glass.
  • These additives alter the way light interacts with the glass, leading to the desired coloration.