Academic journal article Science Scope

"Nor Any Drop to Drink": Students Engineer Solutions for Desalinating Ocean Water

Academic journal article Science Scope

"Nor Any Drop to Drink": Students Engineer Solutions for Desalinating Ocean Water

Article excerpt

Scarcity of water resources is a significant concern owing to overuse and limited supply. This article describes a design-based lesson sequence in which middle school students develop and test methods of small-scale desalination. Students learn about the scarcity of Earth's freshwater resources and the challenges of deriving freshwater from ocean water. The lesson sequence presented here addresses the Next Generation Science Standards (NGSS) while engaging students in an engineering-design project with a civic emphasis (NRC 2012; NGSS Lead States 2013) (see sidebar, p. 48). The sequence can be implemented at any middle school grade level as students are becoming familiar with the changing phases of water and how phase changes occur throughout the water cycle. It addresses NGSS disciplinary core ideas (DCIs) focused on the cycling of water on Earth (DCI MS-ESS2-4) and issues of human impact on Earth's systems and the design of technological solutions (DCI MS-ESS3-4).

Contemporary research in science education supports motivating students by introducing topics they perceive to be relevant to their lives (Osborne, Simon, and Collins 2003). Many such topics are found in the realm of environmental health, or the impact of the environment on human health, which has recently been receiving increased attention as a context for educating future scientists and nonscientists (Keselman et al. 2012). Environmental health also provides an excellent means for demonstrating the connections among science, technology, and society, which is prominently emphasized in the NGSS.

In the design-based lesson sequence described in this article, students are introduced to one of the key environmental-health challenges of the 21st century and then assume an active role in designing a solution to this challenge, thus participating in a fundamental engineering practice identified by the NGSS (see sidebar, p. 48). The sequence of the activity is adapted from the NASA Engineering Design Process Guidelines (NASA 2008). NASA describes the design process in nine steps:

1. Identify the problem.

2. Identify criteria and constraints.

3. Brainstorm possible solutions.

4. Generate ideas.

5. Explore possibilities.

6. Select an approach.

7. Build a model or prototype.

8. Refine the design.

The NASA design process aligns well with the science and engineering practices described in the NGSS. Science and engineering practices are not always linear nor easily broken into discrete steps. Although we describe a linear approach as a pedagogical tool for introducing students to engineering design, we also combine NASA's steps when they naturally reinforce one another.

About the activity sequence

The lesson sequence takes approximately four class periods (see Figure 1). Although discussions are whole-class, design activities are conducted by groups of two to four students. The time each of the steps will take varies depending on the class. Student handouts with detailed instructions, questionnaires, and graphic organizers for structuring the lessons, as well as detailed teacher guides with answer keys, can be found with the online version of this article at www.nsta.org/ middleschool/connections.aspx.

Preparing for engineering: Background knowledge

At the beginning of the sequence, the teacher should frame the learning by briefly stating that students will work on the problem of desalination, or turning salty ocean water into drinking water by removing salt. No detailed explanation of this process is needed at this point as reasons for desalination will be discussed immediately before, and benefits and limitations of industrial desalination immediately after, the engineering activity. Providing a timeline for the activities to be explored will give students scaffolding as well. Before students can engage in designing a desalination device, review or introduce relevant scientific concepts and engineering principles. …

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