2.24. Deposition http://www.ck12.org
FIGURE 2.45
Q:In places with very cold winters, why might frost be more likely to form on the ground in the fall than in the
winter?
A:Frost forms when the air is warmer than the ground. This is more likely to be the case in the fall. In the winter,
the air is likely to be as cold as the ground.
Deposition also occurs high above the ground when water vapor in the air changes to ice crystals. In the atmosphere,
the ice crystals are deposited on tiny dust particles. These ice crystals form clouds, generally cirrus clouds, which
are thin and wispy. You can see cirrus clouds in theFigure2.46.
FIGURE 2.46
Q:Cirrus clouds form only at altitudes of 6 kilometers or higher above sea level. Do you know why?
A:At this altitude, the atmosphere is always very cold. Unless the air is cold, water vapor will condense to form
water droplets instead of ice crystals.
Summary
- In chemistry, deposition refers to the process in which a gas changes directly to a solid without going through
the liquid state. - Examples of deposition in nature include frost forming on the ground and cirrus clouds forming high in the
atmosphere.
Vocabulary
- deposition: Process in which a gas changes directly to a solid without going through the liquid state.
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