Oxidation Reduction Batteries

Last year when teaching about Redox reactions in Chemistry, I could feel my students lack of energy and imagine little floating Z Z Z Z zzzzzz over their heads.  I decided this year to do something a bit more interesting, inspired by a blog called Kitchen Science by the Naked Scientists.  They referenced a YouTube video where the author shows charging his iPod with a fruit battery.

I downloaded one such video, and used it as a jumping off point with my students to inquire, "Can you charge an iPod with a fruit battery?"  We spent 6 days on this short PBL project, and it was completely student driven.  Students were shown the video (hoax), and shown a real example in a Two-Potato Clock that I bought at a garage sale last year for $1.  

After students journaled about how they think the clock works, they chose groups and researched their own food batteries.  They had one day in the computer lab to research and develop their own experimental plan, including safety information, materials lists, step by step instructions, and blank data tables.

We had two days in class to perform experiments, and access to several types of wire, metal plates, alligator clips, multimeters, and potatoes.  Anything else needed to be brought from home.  They also used a Kill a Watt meter to measure how much energy their own phone or iPod charger uses, so they can make a direct comparison between their battery and charging the device.

At the end of collecting their data, we spent one day on direct instruction of what redox reactions are, and how they power the two potato clock example from the first day.  They compared their understanding from their journal on day 1 to their understanding after this activity.

Lastly, students used this new information and photos they took during the experiment to develop a two slide presentation for the class.  They included diagrams / photos of their most successful batteries, and the chemical reaction that was causing the flow of electrons (including identifying what was being oxidized and what was being reduced).  This quick two slide presentation provided a nice quick conclusion of their work, as well as reflecting on what they could have done to make their battery better in the future.

At the end of the class on the final day, we compared the data collected by students (amps and volts), and determined there was no way the initial video was real, it was indeed a scam.  One of my students said we'd "busted" the myth.  I'm just glad we learned about Redox with less pain than last year, and hopefully making more of a memory for the future.