Why an ordinary glass bottle cracks when boiling water is poured into it, but a borosil glass bottle does not?

An ordinary or normal glass bottle is an insulator which means it is a poor conductor of heat. When boiling water is poured into a glass bottle, the inner surface of the glass which is in contact with the hot water heats up and expands according to the coefficient of thermal expansion. But the outer layer of the glass bottle remains cold and does not expand (since glass is a poor conductor, it does not transfer heat quickly). Due to this difference in thermal expansion, thermal stresses arise which eventually leads to cracking.

On the other hand, Borosil glasses have very low coefficients of thermal expansion which makes them resistant to thermal shock, more than any other common glass. Therefore, Borosil glass does not crack when hot liquid is poured into it, but ordinary glass bottle cracks.


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