Hands-on science: (no lab required).After reading "Aliens of the Deep" (p. 8), try this activity to learn how some fish use an air-filled swim bladder swim bladder, large, thin-walled sac in some fishes that may function in several ways, e.g., as a buoyant float, a sound producer and receptor, and a respiratory organ. to maintain buoyancy buoyancy (boi`ənsē, b  `yən–), upward force exerted by a fluid on any body immersed in it. Buoyant force can be explained in terms of Archimedes' principle. . PREDICT Can you make a "fish" floating inside a soda bottle sink to the bottom just by squeezing the bottle? YOU NEED 5 to 7 paper clips * pen cap (without any holes in it) * paper cup * tap water * empty plastic 20-ounce soda bottle, plus its lid PROCEDURE 1 Pull slightly on the outer wire of a paper clip. This will unbend the clip so it becomes a little wider. 2 Wedge wedge, piece of wood or metal thick at one end and sloping to a thin edge at the other; an application of the inclined plane. It is employed in separating two objects from each other or in separating one part of a solid object from an adjoining part, as in splitting the widened end of the paper clip into the opening of the pen cap until only the bottom of the clip is visible. If the paper clip doesn't stay inside the cap when you let go of the clip, widen wid·en tr. & intr.v. wid·ened, wid·en·ing, wid·ens To make or become wide or wider. wid  en·er n. the clip a bit more. Do this until the clip stays inside the cap. 3 Hook two paper clips onto the clip that is wedged wedged - 1. To be stuck, incapable of proceeding without help. This is different from having crashed. If the system has crashed, it has become totally non-functioning. If the system is wedged, it is trying to do something but cannot make progress; it may be capable of doing a few inside the pen cap. This is your "fish." 4 Fill the cup with tap water. 5 Gently place your fish into the cup to see if it floats. If the fish floats on its side, hook on Verb 1. hook on - adopt; "take up new ideas" fasten on, seize on, take up, latch on sweep up, embrace, espouse, adopt - take up the cause, ideology, practice, method, of someone and use it as one's own; "She embraced Catholicism"; "They adopted the Jewish another paper clip. Keep adding clips until the fish floats vertically. Note: The top of the pen cap should stick out of the water. If the whole cap is submerged, unhook one paper clip at a time until the top of the cap sticks out of the water. 6 Fill an empty 20-ounce soda bottle with water to within roughly 2.5 centimeters (1 inch) of the top. Then, very slowly place your fish--clips-end first--into the water. 7 Put the soda lid on the bottle and tighten the lid. 8 Grasp the soda bottle with both hands. Increase pressure on the bottle by squeezing it. Squeeze the soda bottle until the pen cap sinks to the bottom of the bottle. 9 Release your grip. Observe what happens to the pen cap. CONCLUSIONS 1 What happened to your "fish" when you squeezed the soda bottle? What happened when you released your grip? 2 When a fish descends in the ocean, it is because the increased pressure from the water surrounding sur·round tr.v. sur·round·ed, sur·round·ing, sur·rounds 1. To extend on all sides of simultaneously; encircle. 2. To enclose or confine on all sides so as to bar escape or outside communication. n. the fish results in compression of the air inside the fish's swim bladder. As a result, the fish becomes negatively buoyant Buoyant The term used to describe a commodities market where the prices generally rise with ease when there are considerable signals of strength. Notes: These types of markets can be very volatile as the prices are rapid to rise and fall with investor sentiment. and sinks. How is the pen cap in this experiment similar to a fish that has an airfilled swim bladder? Explain. ANSWERS 1. When you squeeze the soda bottle, the fish should sink to the bottom of the bottle When you release your grip, the fish should float back to the top of the bottle. 2. When you squeeze the bottle, the water pressure surrounding the pen cap increases The increased pressure from the water surrounding the cap results in a compression of the air inside the hollow of the pen cap. As a result, the pen cap, like a fish. becomes negatively buoyant and sinks. |
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