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From hippocampus.org (Approved: helpingnorth), produced by University of California and Monterey Institute for Technology and Education
 
This video slide show is accompanied by text: "Water covers more than 75% of the surface of the Earth. While much of it is in the oceans, lakes and rivers also contain a lot of water. Freshwater lakes are home to a vast array of organisms, including frogs and water bugs. Water bugs are sometimes called water skaters or water striders because they can walk across the water's surface. If a water bug can walk across the water, why can't a frog?
In order to answer this question, we need to know a lot more about the properties of water. A molecule within a sample of a liquid is attracted equally in all directions by other molecules, so there's no net force on the molecule in any direction..."
 
Ages: 12 - 18 License: Proprietary Owner: University of California and Monterey Institute for Technology and Education Found by helpingnorth
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