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2.23: Sublimation

Difficulty Level: Basic Created by: CK-12
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Rock bands often use special stage effects, like the fake fog in this picture. Real fog forms when water vapor in the air condenses into tiny droplets of water. The fake fog shown here formed when solid carbon dioxide changed directly to carbon dioxide gas.

How Sublime!

Solid carbon dioxide is also called dry ice. That’s because when it gets warmer and changes state, it doesn’t change to a liquid by melting. Instead, it changes directly to a gas without going through the liquid state. The process in which a solid changes directly to a gas is called sublimation . It occurs when energy is added to a solid such as dry ice. You can watch dry ice changing directly to a gas in the video at this URL: http://www.youtube.com/watch?v=J8mDGwf-5x0 .

Q: Alyssa’s mom put some mothballs in her closet in the spring to keep moths away from her wool clothes. By autumn, the mothballs were much smaller. What happened to them?

A: Mothballs are made of naphthalene, a substance that undergoes sublimation at room temperature. The solid mothballs slowly changed to a gas during the summer months, explaining why they were much smaller by autumn.

Sublimation of Snow and Ice

Snow and ice may also undergo sublimation under certain conditions. This is most likely to happen where there is intense sunlight, very cold temperatures, and dry winds. These conditions are often found on mountain peaks. As snow sublimates, it gradually shrinks without any runoff of liquid water. At the URL below, you can watch a time-lapse video showing sublimation of snow on the highest mountain in the Andes.

http://www.youtube.com/watch?v=7_p9LOTUIDQ

Summary

  • Sublimation is the process in which a solid changes directly to a gas without going through the liquid state. Solid carbon dioxide is an example of a substance that undergoes sublimation.
  • Snow and ice undergo sublimation under certain conditions. This is most likely to happen where there is intense sunlight, very cold temperatures, and dry winds.

Vocabulary

  • sublimation : Process in which a solid changes directly to a gas without going through the liquid state.

Practice

Read the short article about sublimation at the following URL. Be sure to examine the two graphs comparing changes of state in water and carbon dioxide. Then answer the questions below.

http://astronomy.swin.edu.au/cms/astro/cosmos/s/Sublimation

  1. How is air pressure related to the sublimation of solids?
  2. Other than on Earth, name two places in the solar system where sublimation occurs.
  3. At normal sea level pressure on Earth, at what temperature does solid carbon dioxide sublimate?

Review

  1. What is sublimation? Give an example.
  2. Describe conditions under which snow or ice is most likely to undergo sublimation.
  3. The plastic container pictured in the Figure below is filled with solid air freshener. The solid gradually shrinks after the holes in the top of the container are opened. Explain why this occurs.

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Description

Difficulty Level:

Basic

Grades:

7 , 8

Date Created:

Oct 31, 2012

Last Modified:

Aug 05, 2014
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