This week students turn potatoes into batteries! Using pre-purchased kits (I know, a bit lazy), students will connect wires together with the potato to light up an LED.
This is an example of a electrochemical cell. Higher grade levels can delve deeper into chemical process of how this works.
If you cannot order a kit, buying gauge wire, connect it to alligator clips, and use a zinc nail and copper pennies or plate you can set this up.