![]() ![]() But at the surface, where air and water meet, that's not true water molecules there get pulled down, toward other water molecules, more than up, toward the air. When a water molecule is surrounded by other water molecules, pulling forces are balanced by pushing forces, so it's not pulled in one direction more than any other. The liquid's molecules (small particles) are constantly pushing and pulling against one another with tiny electric charges. ![]() Surface tension is defined as the energy needed to increase a surface area by a certain amount. How "stretchy" the balloon material is determines how much resistance (or, in this case, surface tension) must be overcome by your breath to inflate it. The balloon is more resistant to stretching, and can be a model for surface tension. But for a balloon made of thicker or stiffer rubber, more energy is required to inflate it. That is because the balloon offers little resistance to becoming stretched out as it's blown up. If you've ever blown up different types of balloons, you know it's pretty easy to blow up a balloon made of thin, soft, stretchy rubber. ![]() In this science activity you will make a little raft that is actually powered by surface tension-and use your vessel to investigate how surface tension works! Have you ever wondered why a water strider bug can walk on water? Would you believe it is based on the same reasons soap can clean your dishes? In fact, if you look around you carefully, you can find dozens of interesting phenomena that depend on the surface tension of water. ![]()
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