CHEMISTRY NOW: Prehistoric Carbon Dioxide (Grades 5-8) Print

Objective:

Students will learn about the carbon cycle. Students will be able to use this information to gain an understanding of global warming as it relates to carbon dioxide.


Introduction Notes:

CHEMISTRY NOW: Prehistoric Carbon Dioxide

 

 

Title:

 

 

Prehistoric Carbon Dioxide

 

 

Subject/Topic:

 

 

Carbon cycle and CO2 emissions

 

Grades:

 

 

5–8

 

Standards

Alignment:

 

Science as Inquiry

Earth and Space Science: Earth’s History

Science in Personal and Social Perspectives

 

Time Allowance:

 

 

Two 50-minute periods

 

 

 

Overview and Purpose / Objective(s)

(information, concepts to be learned):

 

Students will learn about the carbon cycle. Students will be able to use this information to gain an understanding of global warming as it relates to carbon dioxide.

 

 

Vocabulary:

 

atmosphere—The Earth’s atmosphere is a layer of gases surrounding the planet and kept intact by gravity; the gases consist of 78% nitrogen, 0.97% argon, and 0.04% carbon dioxide, among others. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

 

carbon cycle—The exchange of carbon between the land, the oceans, the atmosphere, and the Earth’s interior.

 

erosion—The movement of soil, mud, rock, and other particles by wind, water, or ice. Erosion is different from weathering because it involves movement.

 

fossil fuels—Fossil fuels such as coal, petroleum products, and natural gas are repositories of ancient biomass that were formed millions of years ago from the decay of plant and animal matter.

 

global warming—The observed increase in the average temperature of the Earth’s atmosphere and oceans in recent decades.

 

photosynthesis—The process by which green plants create energy by absorbing solar energy and carbon dioxide from the atmosphere to produce carbohydrates (sugars). Plants consume and transform these carbohydrates during respiration, which releases the energy contained in sugars to be used as fuel. Plants then release oxygen to the atmosphere, which is used for respiration by humans and other organisms.

 

respiration—The process by which an organism obtains energy through the reaction of oxygen with glucose to give water, carbon dioxide, and adenosine triphosphate (ATP; energy).

 

Materials (Students will be working in groups of two):

       splash-proof goggles

       Student Worksheet

       3–4 pieces of chalk (NOT dustless chalk)

       mortar and pestle to crush chalk

       ¼ cup vinegar (either red or white)

       2 small beakers, graduated cylinders, or small glass jars

       a few scales, to measure mass

 

Activity/Engagement:

(reinforcing lesson, making real-world connection)

 

Part 1—Pre-Activity Engagement:

 

The first part of this lesson is to discuss with students the importance of carbon: 

What are some things we know of that contain carbon?

 

This can lead to a discussion of carbon:

 

Teachers’ Notes: All living organisms are made from the carbon atom. In fact, 18% of our bodies are made of carbon! Carbon atoms continually move through living organisms, the oceans, the atmosphere, and the Earth’s crust. This movement is known as the carbon cycle, which can take millions of years to complete.

 

Discuss with the class the carbon cycle as it relates to humans—that we exhale CO2.

Just as we are part of the carbon cycle, other animals are, too!

 

The purpose of today’s lab is to find out how the carbon in chalk could be carbon from millions of years ago. To begin, ask the students: What are the substances in chalk?

(Answer: calcium, carbon, and oxygen—calcium carbonate.)

 

Background information: The calcium carbonate in chalk is mined from various parts of the world, such as the White Cliffs of Dover in the UK. The Cliffs are composed of calcium carbonate sediment from the shells of ancient sea creatures that sank to the bottom of the ocean. The shells are made from carbon found in the oceans because oceans absorb carbon dioxide from the atmosphere and sea creatures use it. So…if carbon dioxide was exhaled by animals millions of years ago, and it was absorbed by the ocean, and then a sea creature used it in its shell, and then the shell was broken up and became part of the White Cliffs, and then calcium carbonate mined from the White Cliffs was used in this chalk…ancient carbon could be in this chalk! 

 

Part 2—Procedure:

 

1. Ask students to think of ways to design an experiment that would determine that chalk is composed of carbon, oxygen, and calcium.

2. After discussing the carbon cycle as a class, prepare students for the experiment by explaining the setup and procedure.

3. Have groups label their two beakers or small glass containers as Container #1 and Container #2. Have them weigh each container empty and record the weight.

4. Using the mortar and pestle, crush the chalk into as fine a powder as possible.

5. Have students fill Container #1 with about four tablespoons of the crushed chalk. Have them fill Container #2 with ¼ cup of vinegar.

6. Using the scale, have students measure the mass of Container #1 and Container #2, subtract the empty weight, and record the result on their worksheets.

7. After students record the mass of the two substances, have them pour the vinegar onto the crushed chalk and observe the chemical reaction. 

 

(Note: CaCO3 {chalk} + 2 CH3COOH {vinegar} = CO2 + H2O +Ca(CH3COO)2 {calcium acetate})

8. Have students record the mass of the reaction products (water + calcium carbonate in Container #1). (Note: the mass of the reaction products should be less than the original combined mass of Container #1 and Container #2. This is because the chemical reaction between the calcium carbonate and the vinegar released some of the carbon that was stored in the chalk into the atmosphere.)

9. Have students describe the chemical reaction in qualitative terms on their worksheets—How did the reaction look?  Smell?  Sound?

 

 
 
 
 

Concluding Discussion/Activities:

 

- Discuss the results of the activity with students by reviewing the worksheet answers as a class:

 

- Did students find that adding vinegar to crushed chalk released some of the carbon contained in the chalk?

- Do they understand the chemical reaction?

- How is it possible that the carbon contained in the chalk is the same carbon that was present in the environment in ancient times?

- Where is this carbon now?

- Why are engineers concerned about carbon in the atmosphere?

- What is global warming, and what can you do to help?



Chalk Worksheet

 

1. Draw a picture of your experimental setup below. Label the container with the crushed chalk, the container with the vinegar, and the location of carbon atoms before the experiment.

 

 

 

 

 

 

 

 

2. Record the mass of the empty containers. _________________

3. Record the mass of the crushed chalk (Container #1; mass with contents minus empty mass). _________________

4. Record the mass of the vinegar (Container #2; mass with contents minus empty mass). __________________

5. Record the mass of the reactant CO2 + water + calcium compound after the experiment has been carried out. _________________

6. By adding vinegar to the crushed chalk, how much carbon was released?

 

Hint: Add the mass of the crushed chalk and the vinegar before the experiment was carried out. Subtract from this value the mass of the reactant products. ____________

 

7. Write the chemical reaction that occurred between the crushed chalk and the vinegar

____________ + ____________ => ____________ + ___________ + _____________


8.
Explain the reaction resulting from the addition of vinegar to chalk:  What happened when you added the vinegar? What resulted from this reaction? What did you see, hear, and smell?

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

 

 

9. Explain why people are concerned with the rising level of carbon dioxide (CO2) in the atmosphere. What are engineers doing to rebalance the carbon cycle? What can you do to help rebalance the carbon cycle? 

___________________________________________________________

___________________________________________________________

___________________________________________________________

___________________________________________________________

 

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