http://www.ck12.org Chapter 2. Matter
2.24 Deposition
- Define the change of state called deposition
- Describe examples of deposition in nature.
The leaf-like pattern on the glass pictured here is as beautiful as any work of art. It formed on a windowpane on a
very cold winter night. Do you know how it formed? The answer is deposition.
What Is Deposition?
Depositionrefers to the process in which a gas changes directly to a solid without going through the liquid state.
For example, when warm moist air inside a house comes into contact with a freezing cold windowpane, water vapor
in the air changes to tiny ice crystals. The ice crystals are deposited on the glass, often in beautiful patterns like the
“leaves” on the window above. Be aware that deposition has a different meaning in Earth science than in chemistry.
In Earth science, deposition refers to the dropping of sediments by wind or water, rather than to a change of state.
Examples of Deposition in Nature
Deposition as a change of state often occurs in nature. For example, when warm moist air comes into contact with
very cold surfaces—such as the ground or objects on the ground—ice crystals are deposited on them. These ice
crystals are commonly called frost. Look at the dead leaf and blades of grass in the Figure 2.45. They are covered
with frost. If you look closely, you can see the individual crystals of ice. You can watch a demonstration of frost
forming on the side of a very cold can at the URL below. (Click on the multimedia choice “Ice on a Can.”). The
ice in the can has been cooled to a very low temperature by adding salt to it. If you want to do the demonstration
yourself, follow the procedure at the URL. http://www.middleschoolchemistry.com/lessonplans/chapter2/lesson4