I planned a lesson on the water treatment process—focusing on water filtration and the design of water filters—to a small group of approximately six fourth grade students.

 

My goal in teaching this lesson was to supplement/compliment what the students are learning in class by allowing them to engage in a deeper exploration of the human relationship to the water cycle.  I sought to emphasize this connection through the inclusion of an engineering design component.

 

I initially struggled to plan my lesson, because there is a highly structured science program in the classroom.  The students have been studying the water cycle since September, and conduct frequent investigations involving stream tables.  While I aspired to plan something more hands-on and application based, I was also wary of straying too far from the curriculum.  I ultimately selected water filtration as an appropriate alternative.  The connection to the water cycle is explicit, and also ties into a field trip that the students took to the Fairmount Water Works earlier this fall.  During the trip, the students learned that the Water Works had closed because it was exclusively a pumping station and did not have the capacity to filter/treat or purify water.

 

However, when it came time to plan my lesson I was torn once again.  As I researched filtration, its place in the water treatment process, and how to demonstrate it, it began to seem like too much to tackle in forty-five minutes; I did not want to overcomplicate or oversimplify the lesson.  I decided to take my lead from an introductory genetics lesson that was demonstrated in science methods class.  The professor explained that it is appropriate for teachers to be explicit with students that an explanation is simplified, and intended to expose the underlying concepts.  I plan to follow this approach by stating explicitly that our demonstration will be simplified, that we will be focusing closely on one step in the water treatment process, and emphasizing that we will not be disinfecting the water.

 

My final struggle was deciding whether to structure the lesson as a demonstration or to challenge the students to design their own water filters.  I ultimately chose to combine these options by conducting a demonstration with the group to explain the design/testing processes as an introduction to a student design challenge.