- 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.