Part I:

1. Prior to the lesson, prepare several tactile molecular models to represent each of the following forms of nitrogen: N, N, NH4+, NO3-. Display for the class the Matter of Fact Notes handout and the Nitrogen Cycle diagram onto overhead transparencies (optional). Set up seven stations evenly spaced around the classroom. Place a bowl of gumdrops, toothpicks, and a die at each station. Post the station instructions above each station.
2. Distribute the Matter of Fact Notes handout. Complete the handout with the class. As you review the different forms of nitrogen, show students examples using molecular models. Identify the type of atoms in each molecule.
3. Show students the Nitrogen Cycle diagram. Review each step of the nitrogen cycle.
4. Introduce the activity, What Goes Around, Comes Around. Explain to students that there are seven different stations around the classroom. Each station represents a “reservoir” for nitrogen in the nitrogen cycle. Tell students that in this activity they will act as nitrogen atoms moving through the nitrogen cycle. They will start as a pure form of nitrogen. In this form, they are a single atom. Hold up a single gumdrop. At each station students will role a die to determine how they will transform. Students will create a model of the different forms of nitrogen using the toothpicks and gumdrops provided at their starting station. They will take this model with them as they transform into different forms of nitrogen at each station. Have extra gumdrops on hand for construction of the models. Each color gumdrop will represent a different element, the toothpicks will represent chemical bonds. Students should record the information from each station on their What Goes Around, Comes Around chart. Students may use the Nitrogen Cycle handout to identify each process in the cycle. Briefly review each station and tell students that you will give the signal to switch stations every five minutes and that they should rotate to different stations as determined by the roll of the die at each of their stations.
5. Instruct students to return to their desks and complete the "Think About It" section of the handout. Students may work in pairs. Answer any questions before releasing students to begin the activity.
6. As a class, review the "Think About It" section of the handout. Lead a class discussion to highlight the following “big picture” concepts:
   • There is a limited amount of nitrogen in the environment. Nitrogen changes forms as it moves through different stages of the nitrogen cycle.
   • Nitrogen does not move through the cycle as a single atom, but in stable compound and molecule forms.
   • Bacteria play an important role in ammonification, denitrification, fixation, and nitrification. Without bacteria, the nitrogen cycle would cease to be a productive cycle.

Part II: Review

1. Prior to the review activity, divide the class into two equally sized groups based on an observable trait. For example, distribute paper streamers or divide the group by gender.
2. Introduce students to the review activity, Molecular Shuffle. Explain that in this activity, you will reveal different molecular formulas, including atoms, molecules, and compounds. After each chemical formula is revealed, students will scramble to create a group that accurately represents the atoms in the chemical formula.
3. For example, if the formula NO (nitric oxide) is revealed, a student with a green paper streamer will link arms with a student who has a blue paper streamer, to represent the two different elements bonded together. If the formula is HO (water) two green and one blue or two blue and one green will link together. If a student is unable to find a group they are “out” and can watch the activity from the sidelines. Any incomplete groups are also “out.” If you announce a single atom, the students must stand at attention and yell “I’m an atom!”
4. Play the review activity, incorporating each form of nitrogen. Supporting presentation slides for the Molecular Shuffle can be found in the Essential Files portion of this lesson.

Variations

• Instruct students to use arrows and symbols to record their movement through the nitrogen cycle. Combine each student’s unique path using different colors on a shared class diagram.
• Make the review activity, Molecular Shuffle, increasingly challenging. As students become familiar with the different forms of nitrogen, call out the name of the molecule only. Students must determine the chemical formula quickly before gathering into groups. Add oral responses for students to categorize elements as micro or macro nutrient, or increase the complexity of chemical formulas, using examples like calcium nitrate Ca(NO).

ELL Adaptations

• The addition of the complex terms and science concepts can make learning even more difficult. Write down key terms so students can see them and connect them to the spoken word.
• Demonstrate activities in front of class to ensure that English language learners can see the procedures before engaging in an activity. Pair ELL students with partners who are English proficient and have a good understanding of topics being taught in class.