TOPS #13 Cohesion / Adhesion

Begin with soapy water, fresh water, corn oil and rubbing alcohol. The way these simple liquids heap together, roll down wax paper, creep up glass, and soak through paper towels, says much about cohesion, adhesion, surface tension and capillary action. To understand the origin of these forces, your students will assemble a paper model cleverly mimicing the behavior of hydrogen bonds that hold water together. They'll extend these ideas to explain how colors separate by ink spot chromatography; to understand why oil slicks disperse on water with the addition of soap; to account for the elegant surface geometry of soap films colored by glorious interference patterns.