The engineering section of 8th grade Applied Math Lab (AML) has just finished a unit on structure building. Using a required number of newspaper sheets, students worked in groups to create a structure that could withhold the weight of one small book, two small books, a math book…?!, a dictionary…?!, two dictionaries…?!, all of this combined, and more! Students followed a design process that included building, testing, evaluating, and redesigning.

parts of a battery

On Wednesday, October 21^st, the 8^th grade class A created actual working batteries out of nothing but copper rods, zinc coated nails, and lemons. The lemon batteries were connected to LEDs by alligator clips, and the LEDs actually lit up! You might wonder how a plain old lemon can power a light. It all has to do with the acid in the lemon juice. Normal batteries work by having an anode, which is the + side, and a cathode, which is the – side. The anode and the cathode are separated by an acidic solution, which contains positively and negatively charged ions. An ion is an atom that has gained or lost one or more electrons. The positive ions are attracted to the cathode (+ attracts –) and are called cations. Likewise, the negative ions are attracted to the anode and are called anions. The acid is known as an electrolyte because it conducts electricity. This is because of the presence of ions. In our lemon batteries, the copper rod acted as an anode, the zinc coated nail acted as a cathode, and the lemon juice acted as the acid. We connected all 14 of our lemons, linked it up to two LEDs, and turned off the lights. The attached pictures capture the moment that they were lit. To quote a famous man: “It’s Science!!!”