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Carbon Dioxide - Sources and Sinks

Windows to the Universe

In this lab activity, students use a chemical indicator (bromothymol blue) to detect the presence of carbon dioxide in animal and plant respiration and in the burning of fossil fuels and its absence in the products of plant photosynthesis. After completing the five parts of this activity, students compare the colors of the chemical indicator in each part and interpret the results in terms of the qualitative importance of carbon sinks and sources.

Activity takes about three 40-min lesson periods and some preparation. Additional materials required.

Learn more about Teaching Climate Literacy and Energy Awareness»

ngssSee how this Activity supports the Next Generation Science Standards»
Middle School: 3 Cross Cutting Concepts, 3 Science and Engineering Practices
High School: 1 Disciplinary Core Idea, 1 Cross Cutting Concept, 2 Science and Engineering Practices

Climate Literacy
About Teaching Climate Literacy

Biogeochemical cycles of greenhouse gases / Carbon cycle
About Teaching Principle 2
Other materials addressing 2d
Natural processes of CO2 removal from atmosphere is slow; Long residence time of some GHG
About Teaching Principle 4
Other materials addressing 4g
Human activities have increased GHG levels and altered global climate patterns
About Teaching Principle 6
Other materials addressing 6c

Energy Literacy

Environmental quality is impacted by energy choices.
Other materials addressing:
7.3 Environmental quality.
Movement of matter between reservoirs is driven by Earth's internal and external sources of energy.
Other materials addressing:
2.5 Energy moves between reservoirs.
Greenhouse gases affect energy flow through the Earth system.
Other materials addressing:
2.6 Greenhouse gases affect energy flow.

Excellence in Environmental Education Guidelines

2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:B) Changes in matter
Other materials addressing:
B) Changes in matter.
2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:C) Energy
Other materials addressing:
C) Energy.
2. Knowledge of Environmental Processes and Systems:2.2 The Living Environment:D) Flow of matter and energy
Other materials addressing:
D) Flow of matter and energy.
2. Knowledge of Environmental Processes and Systems:2.4 Environment and Society:A) Human/environment interactions
Other materials addressing:
A) Human/environment interactions.

Notes From Our Reviewers The CLEAN collection is hand-picked and rigorously reviewed for scientific accuracy and classroom effectiveness. Read what our review team had to say about this resource below or learn more about how CLEAN reviews teaching materials
Teaching Tips | Science | Pedagogy | Technical Details

Teaching Tips

  • The educator should be well informed about the carbon cycle, sources and sinks. See, for example, this site from Vision Learning: http://www.visionlearning.com/library/module_viewer.php?mid=95&l=
  • Activity is very focused on the mechanics of the experiments and doesn't require the student to understand the bigger picture and the reason for doing this experiment. Educator should include a teaching unit on the carbon cycle to tie this experiment into the bigger picture.
  • Teacher prep time is extensive. The activities require equipment and supplies commonly found in a chemistry lab, except for the indicator Bromothymol blue and a sprig of Elodea (available in pet stores as an aquarium plant).
  • There are six test tubes involved:
    A: control - 1/3 full of BTB;
    B: test for Part 1 - 1/3 full of BTB;
    C: test for Part 2 - 1/3 full of BTB;
    D: test for Parts 3 and 4 - 1/3 full of BTB, wrapped in foil, sprig of Elodea;
    E: test for Part 5 - 1/3 full of BTB;
    unmarked: vinegar and baking soda.

About the Science

  • Lab demonstration of the main carbon dioxide sinks and sources using simple materials.
  • Large conceptual gap between the actual experiments and their interpretation.
  • While the science here is basic and well established, without a full understanding of the workings of bromothymol blue (BTB), the vinegar-baking soda reaction, plant photosynthesis and animal/plant respiration, the links to CO2 sinks and sources may be lost on students.

About the Pedagogy

  • A hands-on activity with well-documented steps; leads groups of four students to consider the concepts of respiration and photosynthesis and their relationship to some of the carbon sources and sinks that exist on our planet.
  • It does, however, make some pretty dramatic leaps from these results to their interpretation.
  • Minimal assessment strategies provided.

Technical Details/Ease of Use

  • The instructions, including the four figures, are clear.

Next Generation Science Standards See how this Activity supports:

Middle School

Cross Cutting Concepts: 3

Systems and System Models, Patterns, Cause and effect

MS-C4.2: Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy, matter, and information flows within systems.

MS-C1.3: Patterns can be used to identify cause and effect relationships.

MS-C2.2:Cause and effect relationships may be used to predict phenomena in natural or designed systems.

Science and Engineering Practices: 3

Planning and Carrying Out Investigations, Analyzing and Interpreting Data, Constructing Explanations and Designing Solutions

MS-P3.1:Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.

MS-P4.4:Analyze and interpret data to provide evidence for phenomena.

MS-P6.1:Construct an explanation that includes qualitative or quantitative relationships between variables that predict(s) and/or describe(s) phenomena.

High School

Disciplinary Core Ideas: 1

HS-LS2.B3:Photosynthesis and cellular respiration are important components of the carbon cycle, in which carbon is exchanged among the biosphere, atmosphere, oceans, and geosphere through chemical, physical, geological, and biological processes.

Cross Cutting Concepts: 1

Cause and effect

HS-C2.1:Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.

Science and Engineering Practices: 2

Planning and Carrying Out Investigations, Constructing Explanations and Designing Solutions

HS-P3.1:Plan an investigation or test a design individually and collaboratively to produce data to serve as the basis for evidence as part of building and revising models, supporting explanations for phenomena, or testing solutions to problems. Consider possible confounding variables or effects and evaluate the investigation’s design to ensure variables are controlled.

HS-P6.1:Make a quantitative and/or qualitative claim regarding the relationship between dependent and independent variables.

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