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Access to healthy food is one challenge facing families, particularly in urban "food deserts," where the availability of fresh fruits and vegetables is limited (Walker, Keane, and Burke 2010). Educators have attempted to address this issue, in part, by developing school-based gardens that provide opportunities for students not only to learn about physical and life science concepts related to growing food, but also "to become familiar with and eat produce that they have grown themselves" (Ozer 2007, p. 853). Yet, in many areas, the growing season is limited to summer when students are out of school. Hydroponics gardening, the method of growing plants in water without soil using mineral nutrient solution (Resh 1998), allows students to grow food throughout the school year and design hydroponics systems that can be effective in classroom and home indoor spaces.
This article presents an integrated science/engineering unit on hydroponics for middle school classrooms during which students design a windowsill hydroponics system for the home using a wicking material to supply water to two lettuce plants. By engaging students in real-world design, the intention is to build their understanding of the crosscutting concept of Systems and System Models through developing and testing a workable hydroponics system, as well as Energy and Matter through optimizing conditions for plant growth (NGSS Lead States 2013).
The hydroponics unit
The hydroponics design unit was developed based on essential components of the Engineering Design Process (EDP) (Groves, Abts, and Goldberg 2014; Hynes et al. 2011). The EDP includes disciplinary core ideas (DCIs) of (a) analysis to define and delimit the engineering problem, (b) synthesis of resources and information to develop possible solutions, and (c) evaluation of a prototype to optimize the design solution (Cross 2000; NGSS Lead States 2013). Figure 1 delineates the lessons and accompanying activities, including opportunities for middle school students to document and represent their learnings, evaluations, and iterations in solving the design problem. Student graphic organizer templates for research, data collection, design generation and evaluation, and presentation are provided online (see Online Supplemental Materials).
This unit, developed and iteratively reviewed by experts in hydroponics, science, engineering, and middle school education, was implemented by four teachers in three schools (e.g., suburban, rural, and urban) in 18 seventh-grade classes. In the suburban and...