Question

A glass test tube containing some water is immersed in boiling water so that the upper end of the test is outside. It is found that water in the test tube does not boil even if it is kept there for a long time. Why?

Answer 1

Water kept in the test tube does not boil when it is immersed in boiling water when its upper end is outside. It is due to the fact that glass is an insulator of heat; it does not allow heat to pass through it and transfer heat to the water present in the test tube. So, the water does not boil which which was present in the test tube.