Materials Science and the Problem of Garbage

Abstract

[ILLUSTRATION OMITTED] Materials science--the science of stuff--has made our lives better by making it possible for manufacturers to supply us with products. But, as a teacher, I'm dismayed that young people enjoying countless consumer goods don't fully understand that much of it ends up in the dump. Landfills and dumps attract vermin, generate leachates (including heavy metals from electronic gadgets), and release greenhouse gases such as methane. Garbage finds its way into our waterways, harming wildlife and creating toxic pollution. Students have misconceptions about materials use. Many may think using bottled water, for example, is harmless because they recycle the plastic empties, but they fail to consider the resources and energy used to produce, transport, and recycle something that, in any case, is superfluous in a city that has safe drinking water. This article describes a series of lessons in which students investigate the technological and engineering ingenuity involved in making materials--and also the environmental ramifications. The aim is to equip students to make informed choices about materials use and disposal. The unit addresses the technology and engineering of materials, including plastics, ceramics, wood, metals, alloys, and composites. The driving question is do we safely dispose of all this stuff? As part of the unit, students act as consultants to help the school green club create advertising that informs the student body about materials, packaging, and the garbage produced as well as the concepts of reduce, reuse, and recycle. The unit, written for five 75-minute classes, aligns with the Next Generations Science Standards (NGSS Lead States 2013; see box, p. 37). Day 1: Introduction Step 1: Engage students in learning Following the principles of Ambitious Science Teaching (Windschitl et al. 2012) (see sidebar and the web), step 1 helps students see that humans manufacture stuff that often ends up in the wrong place, damaging the ecosystem. Students entering the classroom see the question are we doing with all of our garbage? on the smartboard along with images of the Great Pacific Gyre (huge floating garbage patch), including pictures of seals, sea turtles, and seabirds struggling to escape. For 20 minutes, the teacher asks students questions about the images: * Where does all that garbage come from? * What is the primary source of garbage in the pictures? * How did all that stuff end up in one location in the Pacific Ocean? * How can we reduce the amount of garbage in the ocean? On land? * What is all the garbage made of? Do you think it was recyclable? We discuss how ocean currents concentrate garbage in certain locations. We also discuss plastic water bottles: Invariably, some students have them in their school packs. Step 2: Probing background knowledge This step elicits students' prior understanding and ideas without evaluating or correcting their responses. The teacher displays examples of plastics, metals, alloys, ceramics, composites, and various woods, then asks * How are plastics made? * Can you see a difference in the plastics? * Are all plastics recyclable? * What is an alloy? What are common uses of metals? Alloys? What material is used on airplane exteriors? In bicycles? Where do we use ceramics? Concrete and high-tech baseball bats and hockey sticks are examples of composites. Can you suggest what a composite is? Students can be pressed for further discussion and can be asked to elaborate on their explanations, which the teacher puts on the board, grouping and categorizing them to assist understanding. Step 3: Collecting and making sense of data In this step students develop and then test questions and/ or predictions about materials through challenges and problems. …