Definition
The process by which a substance changes directly from a solid to a gas (or from a gas to a solid) without passing through the liquid phase.
Plain English
A solid turning straight into a vapor without melting first, or a vapor turning straight into a solid without becoming liquid in between.
Context Anchor
Seen in aviation weather, icing, and maintenance discussions involving ice, frost, or dry ice.
Derivation
From the Latin sublimare, meaning 'to lift up' or 'raise.' The idea is that the substance is 'lifted' straight from solid form into vapor, skipping the liquid stage entirely.
Why Pilots Care
Sublimation explains how frost can form directly on a cold airframe from water vapor in the air, and how it can disappear without melting. It matters during preflight inspections in cold weather, where ice or frost can appear or vanish without any visible water.
Analogy
Dry ice is a familiar example: it appears to shrink and give off gas without leaving a puddle. That direct solid-to-gas change is sublimation.
Grounding Statement
Think of dry ice: it gives off vapor without leaving any puddle behind. That is sublimation.
Intuition Check
Do not assume a solid must always melt before it can go into the air. In sublimation, the solid changes directly into gas.
Example Sentence 1
Frost on the wings can form by sublimation when water vapor freezes directly onto the cold metal surface.
Example Sentence 2
Carburetor ice can sublimate back into vapor once heat is applied, restoring normal engine operation.