This is one of the first experiments I do with my fourth grade class, with the intention of having them practice science skills instead of learning a chemistry concept. (Although an introduction to the term "cohesion" doesn't hurt, does it?) This investigation asks pairs of students to see how many drops of water they can fit on various coins.
This is a four-page student packet. It guides students to make predictions, conduct a simple investigation, and answer questions based on their observations. They also have to think about why it's important to make repeated trials, handle materials appropriately, and be careful in their methods.
I did this experiment with the students over two 45-minute science sessions. We spent the first session reading the packet, clearing up misconceptions, and I demonstrated how to put water droplets on the coins to add as many as possible. Most student pairs were able to complete the experiment during the next day's session.
In order to complete this investigation, each student pair will need a cup of water, a pipet, a penny, a nickle, a dime, a quarter, and a half-dollar. (Make sure you have plenty of paper towels as well!) I used the plastic coins that came with my school's math manipulatives kit, but real coins would work as well. (One of my students even wanted to compare a real quarter to the plastic quarter, just to see which one would hold more water!)
Thanks for looking! I hope you find this useful.