Sublimation is the process in which a solid changes directly into a gas without first becoming a liquid.
Key points:
- Happens when particles of a solid gain enough energy to break free and enter the gaseous state directly.
- It usually occurs at low pressure or with substances that have weak intermolecular forces.
- The reverse process (gas → solid without liquid) is called deposition.
Examples of Sublimation:
- Dry ice (solid CO₂) → changes directly into carbon dioxide gas.
- Naphthalene balls (used to repel insects) slowly disappear by sublimation.
- Iodine crystals → form purple vapor when heated.
- Camphor → used in religious rituals, disappears without melting.
Importance:
- Used in freeze-drying food and medicines.
- Applied in purification of substances (like iodine and camphor).
- Plays a role in the water cycle (snow/ice sublimating directly into water vapor).