Class Activities
Activity #1 — Photosynthesis Role Play
Students have learned the equation for photosynthesis since the fifth grade, but students often don't understand that the process is a multistep reaction that takes place in different locations in the chloroplast. Students will learn the two-step equation by having each student portray an electron or an atom of hydrogen, carbon or oxygen.
Equation 1, Water Oxidation: 2 H 2O + light —> O 2 + 4 H + + 4 e -
Equation 2, Carbon Dioxide Reduction: 6 CO 2 + 24 H + + 24 e - —> C 6H 1 2O 6 + 6 H 2O
The first step of this activity is to teach students about oxidation and reduction. One student volunteer will portray a hydrogen atom with 1 valence electron. Students will be given a necklace of Velcro that represents the outer shell of valence electrons. I will demonstrate oxidation by removing the one valence electron from hydrogen. I will demonstrate reduction by giving the electron back to the hydrogen atom. These are crucial concepts to understand for further study of photosynthesis. Next, student volunteers will form two water molecules (4 H students, 2 O students, and crepe paper for bonds) and demonstrate water oxidation. One student will portray the Sun, by breaking the bonds and the students will reassemble into an oxygen molecule and four hydrogen ions, each with an electron removed. The fate of the four electrons liberated by the splitting of water will be the transition into our investigation of the electron-transport chain and the Calvin Cycle.
Activity #2 - Carbon Neutral Cars?
It is now hip to be carbon neutral. Going carbon neutral means that you do not add to the amount of carbon dioxide that is currently in the atmosphere. This is not a easy thing to do. An average house can add over 39,000 pounds of carbon dioxide to the atmosphere each year, and driving a car 10,000 miles produces 8,000 pounds of carbon dioxide. Going carbon neutral involves using renewable energy sources that don't add to atmospheric carbon dioxide levels. This is not always possible, though, if you travel by airplane. New companies have sprung up to sell carbon offsets, which go toward reducing carbon dioxide emissions elsewhere. For example, Terrapass is a company that sells offsets and uses the money to invest in windfarms or biofuel projects [26].
This goal of this activity is for students to determine how many trees are necessary to offset the amount of carbon dioxide given off by various cars. They will determine the amount of carbon stored in a tree to give an approximation of the total amount of carbon dioxide taken up by the tree during photosynthesis. Then, students will calculate the amount of carbon dioxide emissions from various cars. They will compare the values and determine how many trees are needed to offset the car emissions each year.
First, students will measure the height and calculate the area and volume of the tree. An easy way to measure tree height utilizes geometry and trigonometry concepts. A clinometer can be made simply using a clinometer sheet, a straw, weight, and a table of tangents. The clinometers sheet and table of tangents can be found at http://www.globe.gov/tctg/tgchapter.jsp?sectionId=201. A measuring tape can be used to measure the circumference of the tree, normally taken at breast height, or 1.5 m from the base of the tree. The formulas for calculating area and volume are given below.
Step 1 — Measure tree height and calculate tree volume
Tree Height ______ meters
Circumference of tree at chest height (at approx. 1.5 m) ______ meters
Area of tree trunk = (Circumference 2 )/4Π ______ meters 2
Total Volume of tree trunk (Area * Height) ______ meters 3
Step 2 — Estimate the mass of carbon in the tree.
To calculate the amount of carbon in kg, we need to use the density (D) of wood and volume (V) of the tree.
Sample Tree Densities
White Oak: 0.68 g/cm 3 Scotch Pine: 0.53 g/cm 3
Douglas Fir: 0.48 g/cm 3 America Beech: 0.64 g/cm 3
Mass (M) of tree trunk (D = M/V) ______ Total kilograms
40% of the dry weight of a tree is carbon. ______ Kilograms of C
Using this information, how much of the tree is carbon?
Step 3 — Estimate the amount of carbon dioxide emissions.
To calculate the amount of carbon dioxide, we will assume that the car is driven 12,000 miles per year (this is a low estimate).
Calculate the number of gallons of gasoline used per year for the following 4 cars/trucks and their average miles per gallon.
Hybrid — approx 50 miles/gallon Hummer — approx 12 miles/gallon
Pick-up — approx 16 miles/ gallon Mid-size sedan — approx 24 miles/ gallon
Convert the gallons per year to liters per year. 1 Gallon = 3.785 Liters
Calculate the amount of grams of Carbon emitted by the following equation:
(________ L gasoline consumed/yr) * (49.3 g C/L gasoline) = ________g Carbon/yr
Convert the result to kilograms (divide by 1000) and compare to the amount sequestered by your tree.
How many trees would each of the cars require to sequester the amount of carbon produced?
Activity #3 — Energy Action Plans for Home and School
Students will use the internet to calculate the amount of carbon dioxide that their household produces (every year or month). They may use multiple websites to calculate this amount as some variation will occur. Here are some sites that give a good carbon estimation:
- http://www.epa.gov/climatechange/emissions/ind_calculator.html
- http://www.climatecrisis.net/takeaction/carboncalculator/
- http://www.safeclimate.net/calculator/
The students should then do research about the changes that they can implement in their house and what the costs or saving for each change would be. The student's research will be compiled into a report that they will present to their families. The students should keep track of the changes in their household's carbon dioxide emissions over the course of the semester and report changes, challenges and successes.
The students will then research the amount of energy used and money spent by their school building. They will propose ways that money could be saved, and then the students will present their multi-step plan for energy and money saving to the faculty and staff. If approved, the energy-saving strategies will be presented to the entire school and advertised through signs and posters. The students will track their energy savings over the course of the school year. The results of this project will be submitted to the school board and superintendant as a model for how students can develop and carry out a plan of action which provides a savings to the school district and empowerment to the students that they are part of the solution to the environmental problems which our students will inherit.
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