(A) Explain why residual thermal stresses are introduced into a glass piece when it is cooled.(B) Are thermal stresses introduced upon heating? Why or why not?

Yes, they are

Explanation:

A

Assuming that a glass piece is cooled from an elevated temperature, then the internal stresses which are also called thermal stresses, gets inroduced due to result of the difference in cooling rate and that of the thermal contraction that exists between the surface and the interior regions. They can lead to fractures such as thermal shock, as a result, we deem these thermal stresses important.

B

Yes, they are. They are introduced upon heating due to the thermal expansion that takes place