Sublimation

Sublimation

Have you noticed that the moth balls which we place in our cloth cupboards disappear after a few days? But you may still get the smell of those naphthalene balls even after they ‘disappear’. What has happened?

Certain solids change directly to gas without passing through the liquid state. The direct change of a state from solid to gas is called sublimation. On cooling these vapours come back to its original (or) actual state.

For example, dry ice (frozen CO₂), naphthalene, ammonium chloride and iodine sublime. The energy required for this change of state can be derived either from the surrounding or from the heat supplied. Inverse of this process is called deposition, in which gas particles lose heat and change their phase to solid.