Book 7, Question 21
Why Does Frost Paint Windows?
On very cold mornings, windows can wake up covered in ferny, feathery patterns. That is frost, and it is made by invisible water vapor in the air. The vapor turns straight into ice crystals on the cold glass.
More fun facts
- Scientists have a name for water vapor skipping the liquid step and turning into ice: deposition.
- One common kind, hoar frost, is a thin layer of fine, white ice crystals.
- Frost on airplane wings has to be removed before flying, often with special de-icing fluids.
- Some frost, called active frost, keeps forming again after it is wiped away.
- Mars gets frost too. Much of the frost on its south pole is frozen carbon dioxide, not water.
- As Mars frost disappears in summer, it leaves patterns of dark cracks shaped like polygons.
Sources: NOAA, NASA, NASA Science
Questions kids ask
How does frost form?
Water vapor in the air turns directly into ice crystals on a cold surface. This is called deposition.
Does frost happen on other planets?
Yes. Mars gets frost, and much of the frost at its south pole is frozen carbon dioxide.