Question

water has two physical forms,i.e.,ice and steam.why are ice and steam not called the allotropes of water?

Answer 1

Allotropes are different forms of an element and they differ in the way the atoms are bonded.
Diamond and graphite are allotropes of carbon. In diamond each carbon is bonded to 4 other carbon atoms while in graphite each carbon is bonded to 3 other carbon atoms.
The bonding between hydrogen and oxygen in ice and steam are the same. These two only differ in the state, ice is solid while steam is a gas.