Question

The material which does not have fixed melting point is
A. Plastic
B. Metals
C. glass
D. Ceramics

Answer 1

Plastic, metals and ceramics have fixed melting point.The glass liquid transition is the reversible and gradual transition in amorphous materials.

Complete step by step answer:
Glass does not have a fixed melting point rather, as the glass is heated, it keeps softening more and melts slowly over a wide temperature range. The hotter it gets, the easier the glass flows.Glasses don’t have a fixed melting point because they have various components in it. It is just impossible to determine the specific melting point of a glass. Glasses can only be moulded at a very high temperature. It completely melts/liquefies at approximately
$1400^\circ C$ to $1600^\circ C$ depending on the composition of glass. A variety of substances are used in making glass, depending on the intent of use. Mostly sand, lime and soda are most commonly used in making glasses. There are many types of glasses such as bulletproof, ex, tempered, stained, tinted, etc.
The melting point of Plastic is $338^\circ F$ . The melting point of Metals ranges from $3,422^\circ C - 6,192^\circ F$ being the highest in tungsten to mercury having an incredibly low melting point that remains liquid at room temperature but they still have fixed melting points. The melting point of Ceramic is mostly above $1000^\circ C$

Thus, the correct answer is option C.

Note: A process where a solid becomes a liquid is called Melting. We see that glass doesn’t actually melt by itself rather it goes through a glass phase transition. This means when it comes to glass melting, it’s a more gradual process. It doesn’t melt but keeps on softening until it can flow.