Question

some solid change directly into gas on heating without passing through a liquid phase.Give the reason why???

Answer 1

this process is known as sublimation direct change of solid into gas
example sublimation of naphthalene balls

Answer 2

The process of converting solid state directly into gaseous is known as sublimation. For e.g. naphthalene balls dissappear by changing into gas with time
HOPE IT HELPS