Sublimation is the process where a solid directly changes into a gaseous state without passing through the liquid state.
In simpler terms, imagine something solid skipping the melting stage and turning directly into a gas, like steam rising from ice without first becoming water. This transformation occurs when the substance absorbs enough energy to overcome the intermolecular forces holding it in a solid state, allowing it to transition directly into the gaseous phase.
Examples of Sublimation:
Here are some common examples of substances that undergo sublimation:
- Dry Ice (Solid Carbon Dioxide): At room temperature, dry ice sublimates, producing a visible white fog of carbon dioxide gas.
- Naphthalene Balls (Mothballs): These balls slowly disappear over time as they sublimate, releasing a characteristic odor that repels moths.
- Iodine: When heated, solid iodine directly transforms into a purple vapor.
- Ammonium Chloride: Upon heating, ammonium chloride changes directly to gaseous form.
Why Does Sublimation Occur?
Sublimation occurs when the vapor pressure of a solid reaches atmospheric pressure at a temperature below its melting point. At this point, the substance can more easily transition into the gaseous state directly.
Importance of Sublimation
Sublimation has various applications, including:
- Freeze-drying: Used in food preservation and pharmaceutical industries.
- Purification of certain compounds: Sublimation can separate volatile solids from non-volatile impurities.
- Special effects: Used in theaters and movies to create fog or smoke.
