Lab 1: Living in a Carbon World

Introduction:

Carbon is everywhere! Carbon is the fourth most abundant element in the universe and is the building block of life on Earth. Carbon exists in pure forms such as diamonds or graphite or in the millions of different kinds of carbon compounds scientists have currently identified. We use carbon compounds such as wood to build and heat our homes. Carbon compounds are responsible for combustion in the gas tanks of our cars and in the muscles of our bodies. This small, six-proton atomic element known as carbon is central to life, gives us fuel for energy, and is critical to regulating our climate. Carbon compounds can exist as gases, liquids or solids. In the non-living environment, we find carbon compounds in the atmosphere, carbonate rocks, and fossil fuels such as coal, oil and gasoline. In the living environment, carbon atoms form the structural molecular backbone of the important molecules of life: proteins, carbohydrates, lipids and nucleic acids (in addition to other carbon compounds made by living organisms). Carbon is a versatile element; it can exist in very small 2-atom molecules such as carbon monoxide (CO) up to molecules that contain thousands of atoms such as proteins and DNA.

On Earth, carbon compounds circulate through land, the atmosphere, oceans and all the organisms that live there. All of these components comprise the global carbon cycle. As carbon compounds circulate, they are continually converted into new forms of carbon compounds. Biosphere organisms from the largest tree to the smallest microbe have key roles in converting carbon compounds into new forms and in cycling carbon throughout the global carbon cycle.

The global carbon cycle can be subdivided into the Geosphere carbon cycle and the Biosphere carbon cycle. The Geosphere carbon cycle operates at very long, slow time scales of thousands to millions of years. Sedimentation, lithification, tectonics and volcanism are important Geosphere processes that convert carbon compounds into new forms. The Biosphere carbon cycle operates on time scales of seconds up to hundreds of years. Photosynthesis, respiration and combustion are key Biosphere processes that convert carbon compounds into new forms.

In Part A, you will trace the pathway of carbon from the atmosphere into trees where carbon can be stored for hundreds to thousands of years. In Part B, you will go outdoors and measure the amount of carbon in a local tree. In Part C, you will use molecular model kits and Jmol images to explore how carbon compounds are built and how they are transformed into new carbon compounds as the move through the carbon cycle. In Part D, you will learn about combustion, a carbon cycle process that burns fossil fuels. You will analyze graphs and videos to determine if the human activity of burning fossil fuels is changing the chemical composition of the atmosphere.

After completing this Lab, you should be able to:

• explain why carbon atoms can form the basis of millions of different types of carbon compound molecules;
• describe how the carbon atoms in CO₂ absorbed via plant photosynthesis provide the carbon atoms for all of the new carbon compounds a plant produces;
• explain how carbon compounds are transformed in four processes that are critical to the carbon cycle: photosynthesis, cell respiration, biosynthesis and combustion;
• apply skills to measure the amount of carbon in a tree;
• explain how combustion moves the carbon atoms in fossil fuel hydrocarbons into the atmosphere.

Keeping Track of What You Learn

Throughout these labs, you will find three kinds of questions.

• Checking In questions are intended to keep you engaged and focused on key concepts and to allow you to periodically check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
• Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills you should be learning from the lab activities and readings.
• Discuss questions are intended to get you talking with your neighbor. These questions require you to pull some concepts together or apply your knowledge in a new situation.

Your teacher will let you know which answers you should record and turn in.