Which of the following does not have a sharp melting point ?

ANS:B - Glass

Glass does not have a sharp melting point. Unlike crystalline materials such as thoria, ice, and pig iron, which have well-defined melting points at specific temperatures, glass undergoes a gradual softening and transition from a solid to a viscous liquid over a range of temperatures, rather than melting at a single sharp point. This characteristic is due to the non-crystalline or amorphous nature of glass. In amorphous materials like glass, the arrangement of atoms or molecules lacks the long-range order found in crystalline materials. As a result, the transition from solid to liquid is more gradual, with the material becoming progressively softer and more fluid as it is heated, rather than undergoing a sudden phase change at a distinct melting point. Therefore, glass does not exhibit a sharp melting point like crystalline materials do. Instead, it softens and flows over a range of temperatures, making its transition from solid to liquid less abrupt and more gradual.