Question

A piece of chalk can broken into small particsls on harmmering but it is not possible to do so in case of piece or a bar of iron

Answer 1

because the particles are so rigidly paced 
they are very hard and tight
so they cannot be broken

Answer 2

Answer:

Aɴsᴡᴇʀ :

• $\longmapsto$ A piece of chalk can broken into small particsls on harmmering but it is not possible to do so in case of piece or a bar of iron because the particles are so rigidly paced they are very hard and tight so they cannot be broken