Question

A piece of glass is heated to a high temperature and then allowed to cool. If it cracks, a probable reason for this is the following property of glass.
A) Low thermal conductivity
B) High thermal conductivity
C) High specific heat
D) High melting point

Answer 1

Hint: We know that heating will occur slowly on a material with lower thermal conductivity material than that of higher thermal conductivity. Also, heat is conducted through the vibration of atoms in the solids.

Complete step by step answer:
In the question, it’s given that the glass cracks after cooling. Glass will break on heating due to the thermal shock and due to the difference in temperature between the two surfaces, the thermal expansion on one side with respect to another side, stress will be induced in the material. When this stress reaches above the yield strength the material starts to develop the crack.

In a detailed way, we can say that the heat is not distributed properly in a material with low thermal conductivity. When any such material is heated, then the temperature gets increased in the outer surface more than that of the inner part.

The expansion on the outer part is more than that of the inner part. In this situation, stress will get generated. If the body is cooled again then the outer surface will contract more rapidly than that of the inner part. At this stage, the stress gets generated and will crack in the body. So the piece of glass is heated to a high temperature and allowed to cool then there is the low thermal conductivity.

Therefore option (A) is correct.

Note: The glass will get the crack only when the temperature is ${150^0}C - {200^0}C$. Due to high humidity in the temperature and low quality of the glass, it may break. In daily use, the low thermal conductivity materials are used in the insulation.