At the fourth grade level, students may be interested in testing the force of magnets. Place a paper clip into a plastic bag that zips sealed. Use a small magnet, like a disc or bar magnet, to try to move the paper clip around the bag, testing a magnet’s force through plastic.
Tie a string to the paperclip and tape the string down to a table to allow the paper clip to dangle off the side of the table. Hold a piece of paper over the magnet and move both toward the paperclip in an effort to move the paperclip without touching it. This tests a magnet’s force through paper.
Drop a paperclip into a cup of water. Move the magnet closer to and eventually into the water to observe a magnet’s strength through water.