One page lab sheet for students to conduct experiments to determine "how many drops of water will fit on a penny before spilling over the side." Advanced learners I ask to repeat the trials on both the heads and tails side of the penny- making two separate charts of repeated trials for each. I also sometimes have them use pipettes vs. eyedroppers. This creates an inquiry discussion (if you haven't already mentioned it) about variables and constants. You can also take it another step farther by having students graph their results and/or graph their results vs. a partners and/or create a class average and graph (advanced students heads vs. tails in two colors), etc.