Which property of borosilicate glass makes it suitable for thermal shock resistance?
- AHigh refractive index
- BLow thermal expansion coefficientCorrect
- CHigh transparency
- DLow density
Solution
Concept
Low thermal expansion means small thermal stresses, which gives high thermal shock resistance.
Formula
Thermal stress σ = E × α × ΔT
Step-by-step solution
1. Thermal shock means a sudden temperature change. 2. A sudden change causes unequal expansion, which creates thermal stress σ = E α ΔT. 3. Borosilicate glass (with B₂O₃) has a very low thermal expansion coefficient α (about 3.3 × 10-6 /°C). 4. Low α gives low thermal stress, so the glass does not crack. 5. The answer is B.
Explanation
Borosilicate glass contains boron oxide, which gives it a very low coefficient of thermal expansion. When it is heated or cooled suddenly, it expands or contracts very little, so the thermal stresses stay small and the glass does not crack. This is why it is used in labware and ovenware (Pyrex).
Why the other options are wrong
A: Refractive index is an optical property and has no link with thermal shock. C: Transparency is also optical and does not resist cracking. D: Density does not control thermal stress.
Shortcut
Thermal shock resistance means low thermal expansion.
Common mistake
Choosing high transparency or density just because they are common glass properties.
Correct answer: B) Low thermal expansion coefficient