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Surface Tension by Anna Christiansen Cable

3rd Place - Natural Category

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School: Evanston Township High School

Teacher: Daniel DuBrow

This insect is able to stay on top of the water because of a physics property called surface tension. This allows more dense objects, like the insect, to stay on top of substances with a lower density, like the water. Water molecules that are not on the surface are surrounded on all sides by other water molecules, and they are attracted to each other. On the other hand, water molecules that are on the surface are not surrounded on all sides. Each molecular attraction causes the molecules to have less potential energy, which results in the molecules at the surface to have a higher potential energy than the ones underwater. In order for the surface area to increase, water molecules that are not on the surface must be pushed to the surface, but because they have a lower potential energy, this requires a certain amount of energy to do. If the object on top of the water does not have enough energy to increase the surface area, than the object will not sink, just like the insect in the picture.

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