Some substances change from solid to gas without going through the liquid phase. This is called sublimation. Even solid water as snow may sublimate. Penitentes are a high altitude snow formation that results from sublimation.
Why It Matters
- When a substance changes phases (from solid to liquid, or liquid to gas, or the reverse) there is a change in energy. More heat is needed to change from solid to gas than from solid to liquid.
- Water ice sublimates under certain conditions: Usually at high altitude where the atmospheric pressure is lower and energy from the sun is strong. High winds can cause sublimation.
- Snow on a snowfield sublimates when it is very cold and the sun shines directly on the upper layers of snow.
- Sublimation is part of the water cycle, although it’s a relatively small part.
- Dry ice (solid carbon dioxide) sublimates at very cold temperatures.
- Check out the Dry-Ice Bomb video (below) about how to harness sublimation of dry ice. Don’t try this at home!
With the link below, learn more about sublimation. Then answer the following questions.
- Discovery, Dry-Ice Bomb (video): http://dsc.discovery.com/tv-shows/other-shows/videos/time-warp-dry-ice-bomb.htm
- What does solid frozen carbon dioxide do when it is brought out of a freezer?
- Why does the bottle explode when dry ice is left in a closed bottle and why?
- Why does the bottle explode?
- Where do you think sublimation of snow to water vapor is most common?