What is Sublimation and its application

  • Sublimation involves direct conversion of a solid into the gaseous state on heating and vice-versa on cooling with no temperature change without passing through the intervening liquid state.

Example of some other substance which undergo sublimation are; ammonium chloride, camphor, naphthalene, benzoic acid, iodine, etc.

Appications of sublimation

  • In very cold places, the snow does not melt but sublimes directly to vapours.
  • In frost-free refrigerators, ice on the walls of the freezer sublimes when warm air is circulated through the compartment during the defrost cycle.

Sublimation depicted at sub-microscopic level

On heating a liquid, the energy of the particles increases. They overcome the inter-particle force of attraction and turn into a gas or vapour at its boiling point. Boiling point of the liquid is a temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure. Changing the atmospheric pressure can change boiling point of a liquid.

  • For instance water boils on a mountain top at a much lower temperature than at sea level. Atmospheric pressure being less requires lesser thermal energy to get vapour pressure equal to atmospheric pressure.