GAMMILL: When life gives you lemons, make batteries

Hebron Christian School student Doug Loden uses a multimeter to test the voltage produced by his lemon battery. (Submitted photo)
Mike Gammill
Special to the Daily Times Leader

As we continue to practice “distance learning” so that our young people may continue to have meaningful educational experiences, Hebron Christian School offered a home lab activity to supplement recent home studies in electrochemistry. 

Since we are dependent on batteries, both rechargeable and single use, the branch of electrochemistry that concentrates on batteries is very relevant to our day to day lives. 

The basic principle of a battery or cell, is based on the work of Alessandro Volta, who was the first to produce a battery or voltaic pile as he called it, that could produce a steady electric current.  Although Volta’s work was over two hundred years ago, the basic principle of batteries is the same.  Of course today, we know that a battery works from two competing electrochemical reactions, one of which gains electrons and the other which loses electrons.  So how can a lemon support an electrochemical reaction?

To answer this question Doug Loden, an eleventh grade chemistry student at Hebron Christian School, constructed a “lemon battery” to find the answer.  In their simplest form batteries require two different conductors as a conducting fluid or paste (electrolyte). 

The simplest way to produce positive and negative poles, or electrodes is to use a couple of coins.  Because coins vary in composition over time and may have different impurities present, it is possible to use two coins of the same kind for the electrodes. 

Doug chose to take this approach to his experiment. 

Utilizing the E° cell equation learned in the previous week’s “at home” chemistry lesson, Doug predicted a cell voltage of 0.153 volts.  When he constructed his lemon battery he measured 0.370 volts.  This variation from the predicted value was due to different amounts of impurities present in the pennies.  

While variations in impurities in acceptable in high school science, commercial battery manufacturers insist on exact voltages from their batteries that are in agreement with predicted values.  Also the half reactions are separated for greater efficiency in generating electricity.  What can we all learn from this activity?  The basic operation of a single use battery can be done at home with materials one likely has at home.  To learn more about batteries try different fruits for the electrolyte and different metals or coins for electrodes.

Mike Gammill is a high school science teacher at Hebron Christian School.