Educate
Jun. 11, 2010

Capturing Carbon Dioxide

by Austen Saltz

Basalt formations off the East Coast of the U.S. could hold a billion of tons of carbon dioxide, according to a new study in the Proceedings of the National Academy of Sciences. Paul Olsen, of Columbia University's Lamont-Doherty Earth Observatory, takes us to a basalt quarry in New Jersey and explains what makes the rock ideal for soaking up emissions.
 
Note: Another Teachers TalkingScience lesson, Sublime Sublimation, makes an excellent introduction to Capturing Carbon Dioxide, and to carbon dioxide itself.
 
Grade Level: 6th – 8th grade
Subject Matter: Physical Science/Geology
National Standards: NS.5-8.1, NS.5-8.2
 
Overview
One of the leading causes of global climate change is carbon dioxide. Carbon dioxide is a greenhouse gas that traps and stores heat from the sun that would normally escape from Earth’s atmosphere into space. Though some heating is beneficial to life on Earth, too much carbon dioxide in the atmosphere leads to dramatic changes in the Earth’s climate. One important field of research aimed at combating climate change is carbon sequestration. Carbon sequestration is the science of taking carbon dioxide out of the air and storing it away. Scientists have been experimenting with different methods of carbon sequestration through chemical, biological or physical means.
In this activity, students will learn more about carbon sequestration by creating a carbonated beverage out of apple juice and dry ice. This experiment illustrates how carbon dioxide can be stored in a substance. Students will compare and contrast the results to determine if liquid carbonation is an effective method for carbon sequestration.
 
Activity Materials
  • Dry Ice (find local distributors at www.dryicedirectory.com)
  • Leather gloves
  • Straws – one for each student
  • Apple juice -- for best results, make sure juice is very cold
  • Glass cups – one for each student
Note: Before purchasing or handling dry ice, review and follow dry ice safety guidelines.
 
Vocabulary
  • Greenhouse gas: a gas that contributes to the warming of the Earth’s atmosphere.
  • Sublimation: process of changing from a solid to a gas or vapor. When something causes sublimation, chemists say that the solid sublimes. (Students should be familiar with these terms from the Teachers TalkingScience lesson, Sublime Sublimation.)
  • Solubility: the ability of one substance to dissolve in another.
  • Nucleation site: a location where dissolved gas molecules can group together to form bubbles.
  • Carbonation: the process of dissolving carbon dioxide in liquid.
What To Do
1. Begin the lesson by having students watch the Science Friday Web video, “Stashing CO2 in Rocks.” Begin a discussion with the students on why scientists want to store away carbon dioxide.
2. Show students a cup of dry ice and have them make observations. From the Sublime Sublimation lesson, students should know that dry ice is frozen carbon dioxide. Where is carbon dioxide found and how is it produced? What are the effects of too much carbon dioxide in our atmosphere? Continue the students’ discussion on carbon sequestration and why scientists are trying to find ways to store away carbon dioxide.
3. Tell students that they are going to experiment with one method of storing away carbon dioxide by using dry ice. Pour cold apple juice into glass cups and distribute one cup to each student. Have students describe and write down how the apple juice tastes (sweet, cold, etc.) and how it appears (clear, yellow, etc.), using as many adjectives as possible.
4. Have students predict what will happen if dry ice is added to their juice. Using leather gloves, drop a small piece of the dry ice into each cup of juice. Have students use straws to stir the juice continuously. Have students write down their observations and explanations of the effects of the dry ice in the juice.
5. Once the dry ice has fully vaporized and no more bubbling can be seen, have students compare the taste and appearance of the juice. How have the taste and appearance of the juice changed?
6. Leave the cup of juice on a counter overnight and observe the juice in the morning. How have its appearance and taste changed when left exposed overnight? What might happen if the cup were tightly sealed and left overnight? Have students explain why liquid carbonation is or is not a good method for carbon sequestration.
 
What's Happening?
Dry ice is frozen carbon dioxide. Since dry ice is a frozen type of gas, it does not melt into a liquid. Instead, it undergoes a process called sublimation. Sublimation occurs when a substance changes directly from the solid phase to the gas phase -- as chemists say, when a substance sublimes. When dry ice is placed inside a cup of juice, the heat from the juice transfers to the dry ice and causes it to sublime even faster, releasing carbon dioxide gas into the liquid.
 
Since carbon dioxide is somewhat soluble in liquids, a small amount of the gas will dissolve into the juice. This dissolved carbon dioxide makes the liquid slightly acidic, giving it a tart taste. The dissolved carbon dioxide also makes the juice fizzy or carbonated, as evidenced by the random formation of small bubbles throughout the juice. These are bubbles of carbon dioxide that have formed at nucleation sites, or locations where dissolved carbon dioxide molecules have come together to form a gas again.
 
If left exposed to the air, the carbon dioxide eventually will exit the liquid in a gaseous form, in the same way that soda will eventually go “flat.” Liquid carbonation is not the best method to use for carbon sequestration, since the resulting effect is carbon dioxide being released back into the atmosphere.
 
Topics for Science Class Discussion
  • What other ways can carbon dioxide be taken out of the atmosphere and stored?
  • How does the temperature of the liquid affect the solubility?
  • How does the amount of carbon dioxide dissolved in the liquid affect its acidity?
  • What other types of liquids can be carbonated?
Extended Activities and Links
  • Measure the pH of the carbonated juice at different time intervals. Do the acidity levels change as the carbon dioxide is released from the juice? Have students research the correlation of carbon dioxide and acidity on a molecular level.
  • Try carbonating orange juice with pulp, and without pulp. Compare and contrast the number of nucleation sites or bubbles formed. How does the pulp affect the number of bubbles formed?
  • Learn more about the carbon cycle through this interactive online animation.
  • Challenge students to make a lemon soda that retains as much carbonation as possible.
  • Have students research current carbon sequestration projects and create a poster board presentation, illustrating an overview of each project, including its carbon capture methods and effectiveness.
  • Try these climate change activities from the Environmental Protection Agency. They include creating a carbon counter hand-held tool and ways to reduce your emissions.
About Austen Saltz

The views expressed are those of the author and are not necessarily those of Science Friday.

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