Global Carbon Cycling Activity - Modeling CO2 sources and sinks
This activity can be modified for age or ability level. It can also be used as a constructive activity
and be supplemented with vocabulary as the students progress or it could be implemented after
the introduction of the figure for reinforcement. This activity could take anywhere from 10
minutes to 30 minutes depending on the style of the teacher and how much time the teacher has
available.
Materials – M & Ms or something else edible
3 small bowls or plates or napkins for each pair of students
Procedure:
 Students get into pairs – one is labeled “source” and one is labeled “sink”
 Students each start with 20 M & Ms on their plates
 One plate should be placed in the middle between the two and 10 M & Ms are placed on
that central plate
 Tell students that M & Ms represent CO2 molecules

Scenario One: Equilibrium
o Tell “source” student to add 4 M & Ms into the central plate
o Tell “sink” student to remove 4 M & Ms from the central plate
o Repeat for 5 rounds
 Question students using Socratic method.
 What are your observations about the central plate and what do they mean?
 What is equilibrium? Explain in terms of the activity. (Teacher could make
extensions here if trying to connect to precious curriculum or explain what
equilibrium is.)
 Ask for other examples of equilibrium in the world to make connections.
 Does equilibrium always exist in nature? (This might be an open-ended
question that the teacher can revisit through the scenarios or lesson and
allow students’ opinions to change throughout the lesson.)
o After discussion, have students exchange M & Ms so they both have 20 and the plate
has ten.

Scenario Two: Sinks Win
o Tell “source” student to add 4 M & Ms into the central plate
o Tell “sink” student to remove 6 M & Ms from the central plate
o Repeat for 5 rounds
 Question students using Socratic method.
 What are your observations about the central plate and what do they mean?
 Where is the Carbon going? Explain in terms of the activity and refer to the
figure.
 What are carbon sinks? How do we know? (Teacher can incorporate
different C sinks for students to record in their notes)
 Ask for other examples of sinks in the world to make connections.
 What happens if all of the carbon was removed from the atmosphere? (This
might be an open-ended question that the teacher can revisit through the
scenarios or lesson and allow students opinions to change throughout the
lesson.)
o After discussion, have students exchange M & Ms so they both have 20 and the plate
has ten.

Scenario Three: Sources Win
o Tell “source” student to add 4 M & Ms into the central plate
o Tell “sink” student to remove 2 M & Ms from the central plate
o Repeat for 5 rounds
 Question students using Socratic method.
 What are your observations about the central plate and what do they mean?
 Where is the Carbon going? Explain in terms of the activity and refer to the
figure.
 What are carbon sources? How do we know?
 Ask for other examples of sources in the world to make connections.
 What happens if carbon was continually added to the atmosphere?
 What is actually happening now? How do we know?
o Divide the M & Ms equally and eat!

From here, the teacher can refer to other figures to provide evidence, provide evidence
from other sources, or create a research project that allows students to find evidence (be
sure to provide direction in finding accurate, scientific evidence and resources for students)