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SimsDaveion_Chemistry IA (1).pdf - What is the effect of...

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What is the effect of the temperature in bodies of water on dissolved oxygen?Research QuestionWhat is the effect of the temperature in bodies of water on dissolved oxygen?BackgroundDissolved Oxygen is the level of free, non-compound oxygen that is in liquids such as water. The water molecules do notcontribute to the count of oxygens in the liquid because the oxygen in water is bonded to hydrogen. Having a dissolvedoxygen level that is too high or too low can harm the animals living in the water. The dissolved oxygen levels needed tosupport life vary from creature to creature. Smaller animals, such as crustaceans, worms and bacteria need smallerlevels (1-6 mg/L) and larger animals, which are the fish, require larger levels (4-15 mg/L). Dissolved oxygen can comefrom the air that enters water and from plants through photosynthesis (Environmental Measurement Systems).Measuring dissolved oxygen levels can is perhaps the most interesting part of it all.There are quite a few different methods of measuring dissolved oxygen levels. People have used electrochemical sensorsor probes and the colorimetric method, but the most traditional way is the Winkler Method. The Winkler Method usestitration in a water sample to determine the amount of dissolved oxygen. In this method, a bottle is completely filledwith water so that no air can cause the experiment to change (Environmental Measurement Systems). “The dissolvedoxygen in the sample is then "fixed" by adding a series of reagents that form an acid compound that is then titrated witha neutralizing compound that results in a color change. The point of color change is called the "endpoint," whichcoincides with the dissolved oxygen concentration in the sample. Dissolved oxygen analysis is best done in the field, asthe sample will be less altered by atmospheric equilibration.”(Bruckner) The probes that can be used have a muchsimpler process. The Vernier probe, for example, doesn’t require reagents to be able to calculate the dissolved oxygenlevels. This probe can simply be placed in water and it will calculate the level right away, as long as the water is stirred.The amount of dissolved oxygen tends to fluctuate with temperature. With consideration to other factors such aspressure and salinity, the colder the temperature typically the higher the concentration. This is because the higher thetemperature, the more kinetic energy the water has. When the water has a lot of kinetic energy molecules are bouncingaround inside the water. Once heated, the water starts to lose solubility, which causes the water to have less oxygen

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Term
Spring
Professor
carlson
Tags
Chemistry, river water

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