Hello,

Firstly you have to know what is hard solid and soft solid.

Hard solid-In this type of solid the molecules are tightly bonded by covalent bond and it is hard to break. Example of such solids are metal like gold, copper or rubber,lead.

Soft solid-They are opposite of hard having weak covalent and ionic bonds makes it easy to break so they appears as soft. Examples of such solid are paper, sponge, food.

Hope it helps.