Academic journal article Science Scope

No More Leaks! A Process-Oriented Lesson Exploring the Invention and Chemistry of Disposable Diapers

Academic journal article Science Scope

No More Leaks! A Process-Oriented Lesson Exploring the Invention and Chemistry of Disposable Diapers

Article excerpt

High school chemistry can be intimidating to some students, so it is critical that we engage students in nonthreatening preparatory investigations during middle school. Based on the learning cycle model (Bybee and Landes 1990), this lesson invites students to investigate disposable diapers. As they explore the properties of sodium polyacrylate, a super-absorbent polymer used in disposable diapers, and how it reacts when exposed to water and simulated urine (colored salt water), students practice many inquiry skills: observation, measurement, graphing, and data analysis. In addition, the student investigation guide (see Activity Worksheet) models scientific writing, much like what is expected in high school science lab reports, and several extensions are offered for further student research. Through this process, students will have an opportunity to see that chemical research can result in substances with useful applications.

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On the particulate level, the process by which sodium polyacrylate absorbs water is too complex for middle school students. Too often, complex concepts are "dumbed down" for lower ages, which may lead to misconceptions and confusion. Therefore, this lesson focuses on the development of student inquiry processes using an intriguing material (viewed macroscopically), rather than the structure of the polymer and its interactions with water on a particulate level. Students investigate the material in the context of a humorous scenario (leaky diapers); humor can be a powerfully engaging learning tool--one that allows students to stretch their skills.

The process skills associated with this lesson are emphasized in the inquiry standards contained in the National Science Education Standards (NRC 1996, p. 150). This lesson works well at the beginning of the school year, when many students would benefit from a reintroduction to laboratory science skills.

Invitation to learning (Day 1)

Hide a disposable diaper in an opaque box or bag, preferably one big enough to disguise the diaper's size and keep students guessing for a few minutes. Tell the class, "Inside this box is one of humankind's most convenient inventions, something that has made life easier for many people. Do you have any idea what it is?" Students will often suggest items they use every day: a pencil, pen, calculator, cell phone, or laptop. They may guess items that occur naturally, such as magnets or water, which offers the opportunity to discuss what an invention is. If they have trouble guessing, you can offer to answer yes/no questions that students pose. Kids will ask, "Is it made out of paper?" or, "Can you wear it?" These questions/answers will eventually lead them to guessing that it's a diaper. As you pull it out of the box, there are always grins and giggles. Limit the discussion to five to ten minutes.

Once the initial frivolity has passed, ask the class what they know about disposable diapers and list their responses on the board. Some might mention that disposable diapers overload landfills and are not as ecofriendly as cloth diapers. From their experiences as babysitters or older siblings, some students may be familiar with the features of disposable diapers--that they expand when wet or that gel sometimes leaks out of the diaper's lining. They likely know little about the actual materials used in diapers. At this point you can distribute Figure 1 to students and ask them to add any new knowledge about diapers to their items listed on the board. If you plan to incorporate student research on diapers or inventions, you can lead students through a KWL.

Organizing your class into pairs, have students spread old newspapers on their work surface and distribute the items on the materials list (Figure 2). This investigation will be messy, and the paper will help with cleanup. At the end of the lesson, students can gather the disposable materials into the center of the newspaper and take the bundle to the trash can. …

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