Walking on Water

This spider appears to be walking on water because of surface tension. Surface tension is the electric attraction between the water molecules at the surface. The force between the surface molecules is unbalanced because they are not completely surrounded by other water molecules. Therefore, the molecules at the surface of the water are closer together. This causes the water to become “sticky” and act like a “skin”. If you look closely at the photograph, you will see that there are little dents in the water where the spider’s legs are. You may think that the spider is floating, but it is really barely touching the water. Since the force of gravity acting on the spider is less than the surface tension and the spider’s legs are hydrophobic, meaning that they repel water, the surface of the water does not break. The surface tension of water allows insects and spiders to “walk on water”.

Jennifer Tam
Eric Hamber Secondary School, Vancouver BC
Category 1 (High School/CEGEP) 1st prize

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