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

Hint: Conduction is the transfer of heat between two bodies when they are in contact with each other. Glass is an insulator of heat. It is in contact with boiling water. Conductivity happens between two solids.

Complete step-by-step answer:
The process of transfer of heat from one body to another body when they are in contact with each other and at different temperatures. It is a slow process.
The rate at which the heat is transferred through a material is called thermal conductivity.
Below are some examples for application of thermal conduction in our daily life-
(1) The process of transferring heat during the cooking of food.
(2) Transfer of heat in to the clothes from iron
(3) The heat is transferred from hot tea to the cup when the tea is poured into the cup, the cup will also become hot.
(4) The melting of ice in our hand due to the transfer of heat from hand to the ice.
Thermal conductivity can be expressed as the amount of heat which flows per unit time through a unit area with temperature gradient of one degree per unit distance.
We know that glass is an insulator and insulators do not allow electricity and heat to transfer through them so, when glass and boiling water are in contact with each other with the upper end of the test tube open the heat does not get transferred from water to glass. So, the water in the test tube does not get heat.

Note: Conductors are the materials which allows the transfer of heat through them which are in contact with it. This makes the other material also heat. Metals are the example for this.
Insulators are the materials which does not allow heat to pass through it. This will not make other material to get heat. Non metals are the insulators.