Lesson 2: Carbon Moves!

Introduction

Dry Ice

In this lesson you will explore carbon. It is a versatile element, and it is vital for life. In your body, carbon makes up about 50% of your tissues, and about 28% of your bones. That is a lot. Carbon also makes up roughly half of plants.

Carbon's reach goes beyond living organisms. Carbon is found in nonliving objects, like diamond or graphite. Carbon is also in rocks, such as limestone, or in fossil fuels in the rocks (petroleum, coal, natural gas). Carbon is also part of the air you breathe, mostly as the gas molecule CO2. In fact, carbon is almost everywhere. Carbon moves between the hydrosphere (oceans and fresh water), the atmosphere, the biosphere (all living organisms), the lithosphere (earth materials), and even the cryosphere (frozen ground and ice).

The places where carbon is found are called reservoirs. You can think of a reservoir as a container, or a part of Earth, that has an amount of carbon. In CP Carbon Connections you will see how the carbon cycle and earth's climate are connected with where you and your family live — you live on the Colorado Plateau. Explore those connections below.

2a. You are carbon!

Get a card from your teacher. The card identifies a carbon-based molecule such as CO2 gas or sugar, and where that carbon molecule is located. Pretend that you are the carbon atom! Write in your notebook what form of carbon you are, where you are presently "living", and what processes change you to a new form of carbon. Then follow the prompts on the card to direct you to your next location. Keep track of all your movements on your record sheet.

Answer these questions in your notebook.

  1. In which reservoirs did you stay for millions of years before moving to a new reservoir?
  2. In which reservoirs did you stay for just a short period of time?
  3. Turn to a new page in your notebook. Sketch the carbon cycle using the places you "lived" when you played the carbon game.
    1. Draw arrows that show carbon moving between the atmosphere and the hydrosphere, and between the atmosphere and the biosphere.
    2. Label the arrows with the name of the process that is moving the carbon between these reservoirs.

2b. Global Carbon Cycle

Below is a diagram of the global carbon cycle. The numbers in the spheres represent the amount of carbon in the different carbon reservoirs. The numbers in the arrows show how much carbon is moving (termed "flux") from one reservoir to another each year. Scientists measure the amount of carbon stored in reservoirs in "gigatons". Most pick-up trucks weigh around 4 tons. A gigaton is equal to a billion tons. There is a lot of carbon on Earth!

Carbon Flux

Answer these questions in your notebook.

  1. Compare the flux of carbon into and out of the ocean. In which direction does more carbon go? Does this seem large compared to how much carbon goes the other direction?
  2. Compare the flux of carbon between the vegetation and soils (biosphere) and the atmosphere. How are they related?
  3. What do you think the arrows show for "natural flux" versus "anthropogenic flux"?
    "Anthropogenic" means that it's from humans.
  4. If the amount of carbon in the atmosphere is increasing, what do you think is the source of the increase?

2c. Carbon From Water To Air

The global carbon cycle illustrates a lot of carbon flux between the ocean and the atmosphere. You can model this with the following investigation.

Experiment Setup

Materials per student team

Listen to your teacher for instructions. Follow these steps, and record your observations and answers to the questions in your notebook.

  1. You'll use a chemical indicator in this activity. Read below about carbon indicators.

Have you heard of an "indicator"? An indicator shows the amount of something, or how it changes. For example, when you measure temperature, this "indicates" the thermal energy of matter, such as water or your body if you have a fever! You can measure temperatures of solid, fluid, or air. In this activity, you'll use an indicator called Bromothymol Blue Indicator, or BTB. Like a thermometer indicates temperature, the color change in the liquid shows the amount of carbon in the liquid. Yellow indicates more carbon, while blue indicates less carbon. Green is in the middle.

  1. Pour seltzer water about 2-3 cm deep in each of two bottles. Pour gently and carefully down the side. Try not to lose any "fizz." A partner should quickly add 20 drops of BTB. Close the containers immediately, and gently swirl.
  2. Place each bottle on a sheet of white paper. Select one bottle as the control. Write this on the white paper, and do not open or move this bottle.

    It should be yellow. This indicates high carbon in the water.
  3. The other bottle is the experimental bottle. It's the one that you manipulate in some way and then compare to the control. Shake vigorously for 15 seconds. Open the cap to release the "fizz."

    Don't pour any water, but you can tilt the bottle sideways to pour out the "fizz" and gas. Then close the cap.
  4. Repeat shaking and releasing gas 10 more times until no more fizz is in the water. Take turns shaking. Take notes on your observations as you complete these steps. How does the color change?
  5. For seltzer water, sometimes people call it "carbonated water."
    1. What do you think the "fizz" is? If you are stuck, check with another team or with your teacher.
    2. If carbon is moving with the "fizz" which way is the carbon moving? In other words, when you finish shaking, does the water have more or less carbon that at the beginning?
    3. What color change indicates less carbon in the water?
  6. Think back to the reservoirs you have learned about. In this activity, carbon left seltzer water. What process on Earth does this activity model?


2d. Carbon From Air To Water

Dry Ice

Do you know the term “dry ice”? It's a solid form of CO2, like ice is the solid form of H2O. A difference is that CO2 doesn't melt to a liquid like ice. It changes from solid directly to a CO2 gas. The gas is coming off the dry ice in the photograph.

Think about this — what do you think would happen if you put CO2 gas above water? Could that CO2 (gas) go into the water? Perhaps in another science class you did an investigation with respiration — breathing out through a straw into water. That puts CO2 from your breath into the water. But to see that change, again, you'd have to use an indicator.

Watch the video below. The indicator in the water is Bromothymol Blue, or BTB. It makes the water blue. Pieces of dry ice are held above the water in a pouch of foil. If CO2 moves into the water, the water will change to a yellow color. This would show carbon moving into water. What do you see in the experiment?

Because your computer is not online, go to the video folder and open co2.mov in your computer's media player.
  1. Think back to the reservoirs you have learned about. What process on Earth is this activity a model for?
  2. How does the investigation and video model the carbon movement in the global carbon cycle?

2e. Summary

In your notebook, write what you learned about the carbon cycle. Also, describe how you are a part of the carbon cycle or draw yourself into your carbon cycle illustration.