8.2

Question 1

What is glass made of ?

Answer 1

Silica - Silicon (IV) dioxide

Question 2

Why is glass brittle?

Answer 2

The silicon and oxygen atoms are not arranged orderly and some points are weaker. So, when dropped or a force is applied, it breaks.

Question 3

Glass does not conduct electricity. Why?

Answer 3

It is because the atoms are covalently bonded.

Question 4

Fused silica glass

Answer 4

• Silicon dioxide, boron oxide
• High softening point (1700 Celsius)
• High radiation resistance
• Resistant to corrosive materials
• Low coefficient of thermal expansion (does not crack easily when it is suddenly cooled)
• telescope mirrors, lenses, optical fibre

Question 5

Soda lime glass

Answer 5

• silicon dioxide, sodium oxide, calcium oxide
• low softening point (700 Celsius)
• High coefficient of thermal expansion (cracks easily when it is heated then cooled suddenly)
• Less resistant to corrosive chemicals
• Low refractive index (4%)
• bottles, jars for beverages, light bulbs, mirrors

Question 6

Borosilicate glass

Answer 6

• silicon dioxide, boron oxide, sodium oxide, aluminium oxide
• Low coefficient of thermal expansion
• resistant to corrosive chemicals
• high softening point (800 Celsius)
• laboratory glassware, cookware, telescope mirrors, microscope lenses

Question 7

Lead crystal glass

Answer 7

• silicon dioxide, lead oxide, potassium oxide, sodium oxide, aluminium oxide
• low softening point (600 Celsius)
• high density
• High reflective index (PbO)
• lenses and prisms
• x-ray - reduces the operator’s exposure to x-rays radiation