This line shows the equation that would give me the slope of my line. It also shows me an R 2 value. This is a measure of how well the size of my circles correlates with whether they sink or float.
The closer an R 2 value is to 1. My R 2 value is 0. Anything above 0. That means that as one variable goes up, the other one does, too. In this case, I have a positive correlation between circle size and how likely my circles are to float. This seems to support my hypothesis. Objects with a larger surface appear more likely to float than those with a small surface area.
No study is perfect. In this one, I divided my sizes into groups. But it might be better to have even more variability in my circle sizes. I could also try to mimic a water strider better. Water striders are light and their legs spread out in a circle. But their legs are still individual legs. Next time, I might build something a little more strider-like.
Another experiment I might try would involve breaking up the surface tension of the water. For that, I would need a surfactant — a chemical that decreases the attraction between water molecules. Soaps are surfactants. Would adding soap to my water make it harder for my striders to float?
But based on these data, it does appear that objects with a larger surface area are likely to float more often than objects with a smaller surface area. And that is, in fact, how water striders do it. They use their long legs to spread their weight on the water. Each individual leg holds very little weight. Get wide enough, and the surface tension of the water remains intact. And the water strider can keep on striding.
By Bethany Brookshire April 2, at am. Just a tray of water, thin wire and a way to measure it. You can use a ruler or calipers. Here are five of my 60 wire rings.
They are all made of the same length of wire, some are just formed into smaller circles. See the shadows on the larger rings? Sorry, your blog cannot share posts by e-mail. Students will also get a lesson in patience and steady hands as they carefully place paperclips in the glass of water to make the water level rise above the glass and create surface tension. Concepts: Water molecules like to stick close to each other, showing a force called cohesion. Where the water molecules meet the air, their cohesion creates surface tension.
This surface tension creates a thin skin on the water. This skin on the water is strong enough to support lightweight objects. Animals that walk on water spread their weight over a large area so they won't break through the water's skin. Vocabulary: water tension, cohesion, water strider, habitat. This activity is designed for 3rd graders, but could be appropriate in any grade and possibly as a teacher demonstration in the lower grades.
Water striders can be seen on the surface of calm or slow-moving water throughout the continental U. They prefer ponds, vernal pools, and marshes. The water strider's shorter front legs are used for catching and holding onto food. Water striders eat insects and larvae on the surface of water, such as mosquitoes and fallen dragonflies. How do they walk on water?
The first thing you notice about water striders is their rapid skipping across the water surface. How do they stay on the surface? Water strider legs are covered in thousands of microscopic hairs scored with tiny groves. Even in a rainstorm, or in waves, the strider stays afloat. What else do their legs do? As with all insects, the water strider has three pairs of legs.
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