When glass is formed, which of these takes place first? a) the sand turns to liquid. b) the molecules become hard. c) the sand is heated intensely. d) the molecules become disordered.

The correct answer is option C which is, "The sand is heated intensely".

Glass is the allotropic compound of silicon dioxide. For the formation of glass, first of all the sand which contains the silicon dioxide is melted. For this purpose it is heated intensely.

Due to heating at high temperature, it melts. After melting it ifs cooled immediately. In this step molecules become hard without any special pattern formation.

That is why glass is an allotropic compound. Hence correct answer is option C.

14,16 18 reacts with group

the answer is 75.0%.