259902772-Water-is-a-Compound-of-Oxygen-and-Hydrogen.docx -...

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Water is a compound ofoxygenandhydrogen(chemical formula: H2O) with highlydistinctivephysicalandchemicalproperties: it isabletodissolvemany other substances; itssolidform (ice) islessdensethan theliquidform; itsboiling point,viscosity, andsurface tensionareunusuallyhigh for its molecularweight, and it ispartiallydissociatedintohydrogenandhydroxylionsWater is Acolourless,transparent,odourless,liquidwhich forms the seas,lakes, rivers, andrainand isthebasisof thefluidsoflivingorganisms:sodium chloridedissolvesin watercan I have adrinkof water?How do we measure the quality of ourwaters?Doctors use instruments like thermometers and stethoscopes to check on your health. Scientistsuse instruments like Secchi (sek’-ee) disks, probes, nets, gauges, and meters to determine howhealthy the water is. They take measurements of the physical and chemical condition of the waterand the health of the critters that live in it.Scientists collect water in lots of different ways. They use boats to go out in the middle of lakes,they wade into streams wearing rubber boots that go up to their chests, they drop buckets overthe sides of bridges—they’ll do almost anything to get a sample.Water samples aren’t the only things scientists collect. They take photographs from airplanes andeven satellites. They use their eyes to observe what’s happening along streams, lakes, and bays toget an overall sense of the health of the water. They also collect fish, plants, dirt, and aquaticbugs, and study what’s happening on the land that’s next to the water.What do scientists measure?**** The words highlighted in bold are defined in theglossary.Temperature- When you don’t feel well, chances are the first thing someone does is take yourtemperature. Scientists measure water temperature for several reasons. First, it determines thekinds of animals that can survive in a stream. If the temperature gets too hot or too cold for someorganisms, they die. Temperature also can affect the chemistry of the water. For example, warmwater holds less oxygen than cold water. A healthy cluster of trees and vegetation next to astream or river helps keep temperatures cool fortrout and other fish.Dissolved oxygen- Scientists measuredissolvedoxygen, or DO (pronounced dee-oh). This tellsthem how much oxygen is available in the waterfor fish and other aquatic organisms to breathe.

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