Grades K–2 · Earth & Space
How can tiny ice feathers grow on a cold surface?
A cold morning can leave a fence sparkling with tiny ice shapes. Some of this ice grew directly from water vapor, the invisible water in the air.
In the diagramWater vapor can become ice directlyA very cold surfaceVapor joins growing ice crystalsIceTiny ice crystals grow on a cold surface.
On a cold-enough surface, water vapor can become solid ice without becoming liquid first. More water joins the ice, and a crystal grows. The drawing makes these tiny crystals much larger so we can see them.
There is another way for ice to appear: liquid dew can form and then freeze. The two routes end with ice, but they take different steps. A cold surface also needs suitable moisture conditions; cold alone does not promise a frosty coating.
About this explanation
Starting knowledge: Recognize liquid water and solid ice.
Sources
- NOAA National Weather Service — Rime: comparison with frost formation
- NOAA National Weather Service — Frost-Freeze Information