Dinosaur Breath

In this simple demonstration, students will learn about the role of dinosaurs in the carbon cycle and the eventual storage of excess carbon in the form of chalk. They will understand the importance of the carbon cycle.

Background

All animals, including the dinosaurs of Jurassic times and we humans, are part of the carbon cycle. By eating food, animals gain carbon in the form of carbohydrates and proteins. In each of our bodies' cells, oxygen combines with food to give energy for daily activity. Carbon dioxide, a waste product of this cellular metabolism, is released back into the atmosphere when we exhale or breathe.

Some of the carbon dioxide in the atmosphere dissolves and is stored in ocean waters. The oceans act as a storage place or sink for carbon.

Many organisms living in the ocean use the dissolved carbon dioxide to make calcium carbonate () shells. Some of these organisms are large and easy to see (for example, clams and snails), but most of the carbonate shells are produced by the microscopic creatures called plankton.

Floating in all the oceans of the world, plankton absorb vast quantities of carbon in their shell-building activities. They do not live long though. In some places, when they die, their shells fall to the bottom of the ocean floor to form sediments of limestone and chalk. Raised above sea level by tectonic activity, the sediment often forms large rock formations. The white cliffs of Dover are gigantic chalk cliffs originally formed from these types of sediment. Natural chalk is mined from such formations. Much of the chalk sold today is 'dustless' chalk, which is synthetic and NOT composed of natural carbonate. Dustless chalk will not work in this demonstration.

Learning Goals

1. Students will appreciate that the carbon cycle has always been essential for life on earth, just as it is today.
   
   
2. Students will appreciate the role of the oceans as a carbon sink.
   
   

Alignment to National Standards

National Science Education Standards

• Life Science, The Interdependence of Organisms, Grades 9 to 12, pg. 186, Item #1: "The atoms and molecules on the earth cycle among the living and nonliving components of the biosphere."
  
  
• Earth and Space Science, Geochemical Cycles, Grades 9 to 12, pg. 189, Item #1: "The earth is a system containing essentially a fixed amount of each stable chemical atom or element. Each element can exist in several different chemical reservoirs. Each element on earth moves among reservoirs in the solid earth, oceans, atmosphere, and organisms as part of geochemical cycles."
  
  
• Earth and Space Science, Geochemical Cycles, Grades 9 to 12, pg. 189, Item #2: "Movement of matter between reservoirs is driven by the earth's internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of the matter. Carbon, for example, occurs in carbonate rocks such as limestone, in the atmosphere as carbon dioxide gas, in water as dissolved carbon dioxide, and in all organisms as complex molecules that control the chemistry of life."

Benchmarks for Science Literacy, Project 2061, AAAS

• The Physical Setting, Processes That Shape the Earth, Grades 9 to 12, pg. 74, Item #1: "Plants alter the earth's atmosphere by removing carbon dioxide from it, using the carbon to make sugars and releasing oxygen. This process is responsible for the oxygen content of the air."
  
  
• The Living Environment, Flow of Matter and Energy, Grades 6 to 8, pg. 120, Item #2: "Over a long time, matter is transferred from one organism to another repeatedly and between organisms and their physical environment. As in all material systems, the total amount of matter remains constant, even though its form and location change."
  
  

Grade Level/Time

• Grade level: 6 to 9
  
  
• Time:
  
  
  • Demonstration: 10 minutes
    
    
  • Discussion and student questions: 30 minutes
    
    

Materials

• Crushed chalk (do not use dustless chalk)
  
  
• Vinegar
  
  
• Beaker or glass jars
  
  

Procedure

Note: It is strongly recommended that your students have completed Activity 15.

We recommend that this exercise be carried out as a demonstration.

1. Discuss the role of dinosaurs in the carbon cycle and the eventual storage of excess carbon in the form of chalk. If the students have completed Activity 15, have them refer to their final carbon cycle diagrams to help sort out the ancient carbon cycle. Ask students where dinosaurs obtained carbon for their bodies and where the exhaled went. Discuss the following:
   
   
• One of the major sinks for is the ocean. Many organisms living in the ocean use to make calcium carbonate () shells. Over millions of years these shells have broken down into chalk. Chalk is mined to make the chalk sticks used on chalkboards.
  
  
• It is helpful to display some seashells while you talk about their composition.
  
  
2. Take a piece of chalk and talk with students about its composition (it's made of calcium carbonate).
   
   
3. Place crushed chalk into a beaker and add vinegar. By pouring on the vinegar, the chalk releases , possibly the very same that was released during the Jurassic time period. They may be releasing dinosaur breath that was stored in the chalk!
   
   
4. Watch and explain the chemical reaction: chalk + vinegar > [=] exhaled dinosaur breath () + water + calcium compound

Observations and Questions

1. Explain the reaction resulting from the addition of vinegar to chalk.
   
   
2. Explain the carbon cycle and why it is conceivable that dinosaur breath was released when vinegar was added to chalk.
   
   
3. Why does carbon combine with so many different molecules in the carbon cycle?
   
   
4. Describe the carbon pathways from your favorite herbaceous and/or carnivorous dinosaur to the shell of a marine organism and then to chalk. Show at least six steps that the carbon must travel in this pathway.
   
   

Assessment Ideas

• Have students draw a diagram and write an essay for question #4 above.
  
  

Modifications for Alternative Learners

• No modifications required.