The centers going on now include building with blocks,
making waffles from scratch with a waffle iron,
building three-dimensional geometric forms with marshmallows and toothpicks,
and, as described in a previous post, sinking pieces of wood with paper clips.
Repeating the same activity with new groups gives the teacher and opportunity to refine questions and processes towards a better result. You can see this group had a better grasp of the difference between pine and plywood's ability to float paper clips. We even recorded the results of our investigation.