Surprisingly, these seemingly disparate questions are both related to a property of water known as surface tension. The investigations in this activity explore some characteristics of surface tension and demonstrate how soaps and detergents affect surface tension. Scientific Inquiry Students conduct several investigations which illustrate the high cohesive force between water particles and the increasing wettability when a surfactant is used.
Students develop explanations using evidence from their investigation.
They also discuss why it is important that soaps decrease the surface tension of water and wet surfaces more easily. They explain why a string loop floating on the water's surface immediately becomes circular if a drop of detergent is placed in the center of the loop. Students may use mathematics to graph their results from two investigations. Liquid water has the observable property of surface tension. A characteristic property of water is that it has strong cohesive forces and a very high surface tension due to the attractive forces between water particles.