Glass Basics: 17 MCQs with answers

Silicon dioxide (SiO₂)

Silica (SiO₂) is the main glass-forming oxide in most glasses, providing the structural network.

Acid etching

Acid etching (e.g., with hydrofluoric acid) roughens the surface, scattering light and creating a translucent, frosted appearance.

Insulation

Fiberglass is widely used for thermal insulation in buildings and also in composites for boats and car bodies.

Annealing

Annealing is the controlled cooling of glass to reduce internal stresses that could cause cracking or shattering.

Optical transparency

Glass is transparent to visible light, allowing us to see through it while still providing a barrier against the elements.

False

Glass is an amorphous solid, meaning its atoms are not arranged in a regular, repeating pattern.

True

Tempered glass is designed to shatter into small, less harmful fragments, reducing the risk of injury.

Crystalline structure

Glass is amorphous (non-crystalline), so having a crystalline structure is not a property of glass.

To lower the melting point of silica

Soda acts as a flux, reducing the melting temperature of silica from about 1700°C to a more workable 1000°C.

Borosilicate glass

Borosilicate glass (e.g., Pyrex) contains boron oxide, which reduces thermal expansion, making it resistant to thermal shock.

Cobalt oxide

Cobalt oxide is a strong colorant that gives glass a deep blue color, even in small amounts.

It is stronger and shatters into small pieces

Tempered glass is heat-treated to create surface compression, making it about four times stronger and safer as it breaks into small, blunt fragments.

Lead oxide (PbO)

Lead oxide is added to glass to increase its refractive index, making it sparkle and suitable for crystal glassware.

To improve chemical durability

Lime acts as a stabilizer, making the glass more resistant to water and chemicals, preventing it from dissolving.

Fused silica

Fused silica (pure SiO₂) has extremely low optical loss and is ideal for transmitting light signals over long distances.

500-600°C

Soda-lime glass has a Tg around 500-600°C, where it transitions from a hard, brittle state to a soft, rubbery state.

70%

Soda-lime glass typically contains about 70% silica, with the rest being soda, lime, and other additives.