metal (magnetic: iron or steel)
The rest of the supplies: water, wide and shallow plastic container and magnets (of course)!
We used a simple square piece of cardboard and taped our metal cogs to the bottom. We sealed the rest of the boat with tape (just to keep the water from soaking up the cardboard).
Fill your container with about an inch of water. Place your container on your lap while seated on the floor (legs crossed like a pretzel). This will allow the children to reach under the container safely.
Our metal on the bottom of the raft
Place raft in water (The legos were just going along for the the ride....lol) We ran our magnets along the bottom of the container and moved our rafts across the water! Magnetic force fields are pretty strong!
We also completed our worksheets on when a magnet attracts and repels.
Extra fun: We dropped a few hex nuts in the water to see if the magnets would move them, as well. And they sure did!
(Not all hex nuts are magnetic. I have some in brass, stainless steel and zinc. You can drop them all in and see what happens!)