Third grade scientists investigated compasses in lab to kick off their social studies unit on explorers. After reviewing the compass rose, we experimented with the relationship between magnets and compasses. A compass is a lightweight magnet. The needle lines up with the earth’s magnetic field. Then we made our own compasses. We magnetized a nail and placed the nail in a Petri dish that was floating in a bowl of water. We watched the magnetized nail search for North.