Activities
Inquiry-Based Toxic Tour of Bayview Hunters Point
A toxic tour of BVHP will be one of our first activities in this "Science of Environmental Justice" unit, so that students can use the inquiry process to identify sources of toxicity in the community and their impacts on the residents. This activity is a field study involving multiple van stops and some walking through the neighborhood.
Students will first be introduced to the neighborhood and its environmental justice issues via a map of all the toxic sites in BVHP. This map utilizes a key with each different type of toxicity represented by a colored shape. It is immediately evident that BVHP is overwhelmed by toxic sites. In groups, students will identify what each symbol in the key represents, count each type of toxic site, generate a total number of toxic sites, and answer an application question about how the map applies to environmental justice or injustice. Each group will share its findings. I will then introduce the inquiry activity by explaining to students that the purpose of the field study is to tour the area in order to identify sources of toxins and hypothesize as to their possible effects on human health. At each stop, students will divide a page in their field notebooks into three sections: observations of the site, hypothesis of sources of toxicity supported by specific observations, and hypothesis of effects on human health supported by specific observations. Observations in every category can include multiple senses: sight, sound, smell, taste, and touch.
Our first stop will be near the sewage treatment plant. Students will be able to smell the sewage and see the open separation tanks, as well as note the close proximity of housing on the very same block. The second stop will be near the rendering plant and a factory that coats non-stick pans. The rendering plant also has a distinct and unpleasant odor while the factory is full of the noise of industrial activity. Both are close to a busy street where pedestrians are a constant. The third stop will be on a hill where the Potrero Hill power plant and junction of two freeways are in view. The freeways and power plants are both downhill from the Potrero Hill public housing projects and power plant's smoke is clearly and visibly blowing toward the complex. Our last stop will be the Naval Shipyard, where we will have to peer through the fences to observe construction in progress, then walk up a few yards to a dilapidated park and the nearest housing projects. Our last stop will be at Heron's Head Park, where we will be able to see a recycling center, the remains of the now-dismantled power plant, and the park itself. This will pose an interesting contrast as a preview for our next visit to BVHP, when we will be doing habitat restoration at the park.
At the end of each stop, students will share their observations and hypotheses, taking note of observed evidence generated by their classmates that might also work to support their own hypotheses. This debriefing process will help students be increasingly attentive and analytical at each stop as they gain insights from one another regarding the correlation between observations and hypotheses. The conclusion of the field trip will be an assignment in which students must predict the toxicity of BVHP on a scale of one to ten, citing specific observations to support their assessments. After each student has written their evaluation, students will be grouped with classmates who had similar ratings (a 1-2 group, 3-4 group, etc.) and each group will prepare a statement with which to debate the others. We will have a debate with opening statements, rebuttals, and closing statements for each group, then vote at the end for a final rating.
This inquiry will continue at school as students read a summary of BVHP's "State of the Environment" report. Students will compare the findings of that report, and its data, to their own hypotheses and observations from the field study. They will then write final conclusions in which they confirm or revise their own studies.
Modeling the Nature of Toxicity
Students will create models to represent each form of toxicity we study: reactivity, solubility, volatility, and radioactivity. Creating models will help students visualize the chemistry concepts they must learn in order to answer the question, "What makes a toxin toxic?" As previously discussed, in order to understand the reactivity of elements and molecules, students must understand atomic structure, especially electron configuration. To create models of atoms and assess their electron affinity, we will use large red beads to represent protons, large beige beads to represent neutrons, small blue beads to represent electrons, and wire to represent electron shells, onto which we can thread the electrons. Protons and neutrons will be collected in some kind of container, and the wire electron shells will be attached in concentric circles to that container. In pairs, students will use these materials to construct atomic models of the first twenty elements because the orbitals of those twenty are very straightforward and do not overlap across different energy levels. Each element will be presented, including an assessment of its reactivity based on valence electrons and the octet rule. Each atom/pair of students must then find at least one other atom with which they think they can bond. These pairings will also be based on the octet rule, so students should seek out atoms with valence levels complementary to their own. As each pair presents itself, the class will identify which molecules will be stable and which might remain reactive. Molecules that have filled valence shells are stable, those that have unfilled valence shells and are reactive.
Later, when studying the relationship between polarity and solubility, students will utilize the same models. Taking any two atoms, groups of four students will use a periodic table to determine the electronegativity of each. Based on electronegativity values, each group will then identify whether the atoms would form an ionic bond, a polar covalent bond, or a non-polar covalent bond. The models will provide visual clues in that atoms of similar sizes tend to form non-polar bonds, while big-small pairs will result in ionic or polar covalent bonds. Once the type of bond is chosen, students must then attach their atoms to one another in a way that demonstrates the type of bond. For example, an ionic bond would require students to remove one electron from an atom and relocate it on another. A polar covalent bond would require students to shift the electrons toward the atom of highest electronegativity.
While our models for reactive and soluble chemicals will focus on the first twenty elements, the models that demonstrate radioactivity will focus on the last ten. For these radioactive elements, we will use the same materials to represent atomic structure. However, when students build these atoms, the large number of protons and neutrons will be difficult to enclose within the container that represents the nucleus. Any spillover, especially when the teacher jostles the table, will demonstrate an unstable atom. After demonstrating the basic instability of large atoms, we will then create models of several isotopes to analyze the imbalance of protons and neutrons. The last step of this modeling process will be to enact alpha and beta emissions by removing protons and neutrons to see if the stability of the nucleus increases.
The final set of models will also utilize traditional molecule-making sets. In groups, students will build models of three different molecules, and then calculate the molecular mass of each using a periodic table. Each group must then determine which molecule is most volatile, based on the molecular mass. Once the VOCs are identified, the structure of each VOC will be examined and categorized. We will then refer back to our atomic models to identify why the bonded elements have bonded, focusing on the electron configurations of hydrogen and carbon.
After studying the structure and behavior of each type of toxin, students will predict how atoms and molecules in each category might interact with the atmosphere or within a body. These predictions will be used to predict ways and reasons each type of substance is toxic to humans. We will discuss these predictions, then the answers will be revealed in a reading that also reinforces the earlier lessons about the atomic and molecular structure.
Integrating the Principles of Environmental Justice and the Principles of Green Chemistry
In this activity, students will first be presented with summaries of simple case studies that demonstrate a few of the most pertinent principles of green chemistry. In small groups, students will read the case studies and work together to analyze why the chemistry represented is more sustainable than traditional chemistry. Through this analysis, students will be identifying some of the principles of green chemistry. As each group shares, the class will work to identify what principle is at work in the case study. After the class as a whole has recorded their interpretation of the principles, we will read the actual principles that correspond. Students will be paired up to translate each principle into their own words and share it with the class.
Students will individually examine some of the sources of toxicity in BVHP: the power plant, the sewage treatment plant, the rendering plant, and the shipyard. They will be asked to identify which principles of green chemistry are being violated in the process of also disregarding the principles of environmental justice. As each student shares an analysis, the class will identify which specific environmental justice principles seem to best correspond with specific green chemistry principles. The conclusion of the activity will be for students to write a summary of which two or three green chemistry principles they feel best support the principles of environmental justice, why, and how.
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