In class, tension is a hands-on affair

There’s no tension between student and teacher in Julie Smith’s advanced cell and molecular biology class. Or if there is, let’s just say it’s all on the surface.

Smith’s 11th- and 12th-grade students recently completed a series of labs on such topics as solubility, specific heat capacity, evaporative cooling, cohesion, adhesion, and, of course, surface tension. Smith allows two of her students,  juniors Armaan Dhaliwal and Audrey Aspegren, to explain:

“The paper clip in this picture is demonstrating one of the properties of water. A paper clip does not float—instead, due to the unique nature of water molecules, the paper clip is being held up by the surface tension of the water in the cup.

“The weight of the paper clip does not break the surface tension of water, so the paper clip appears to be ‘floating’. Because water is a polar molecule, meaning it has one slightly more negative end and one slightly more positive end, the water molecules are attracted to each other. This creates a bond that is harder to separate, which results in surface tension.

“This also occurs in nature. For example, water strider insects utilize this technique to enable them to ‘walk on water.’ ”