Many students have made batteries from potatoes and citrus fruits, but this experiment offers a twist on the battery theme. This experiment requires distilled water, salt, vinegar, copper and iron rods, alligator clip wires and light bulb holders with light bulbs. A student may create several batteries by filling a beaker with distilled water and placing a copper and iron rod in it. The second battery consists of distilled water with about 20 percent salt dissolved into it. The third is simply vinegar poured into a beaker. The student discovers which one is the most effective by clipping an alligator clip wire to the copper and iron rods in each beaker and then touching the other ends to the light bulb holders. Students should determine which batteries were effective for lighting up the bulb and why.
Students often make a compass in school by magnetizing a needle and floating it in water with a cork. The following idea makes a compass that is more comprehensive and powerful. It is also slightly more complicated and well suited to intermediate-age students. The experiment requires a sharpened pencil, a large lump of clay, a screw-top bottle cap and two rectangular block magnets. The student holds the magnets next to each other to find the faces that stick together. He then tapes the magnets to opposite sides of the bottle cap with the attractive sides facing inward. He pushes the pencil, eraser end down, into the clay and balances the bottle cap on the pencil's tip. The cap should turn to orient itself with the poles.
This experiment demonstrates how vibrations carry sound. Media that vibrate freely carry sound further than those that naturally sit still. A student needs a plastic tub of water, a wooden box and a waterproof tape recorder. The student records whatever music she likes (adhering to school rules for appropriateness) on the recorder and places it in the wooden box, then in the water tub, and then listens to it in the open air. Experiment judges and observers press their ears to the box and tub to gauge how the sound travels. The student's experiment board should discuss which media carried the sound best and why.