|MadSci Network: Environment & Ecology|
Dear Gabby thanks for your question. Oil spills are indeed bad because of the dangers to wildlife that get contaminated by the oil. Birds lose their abilities to fly and often drown in a rather miserable and lingering way. Crude oil spilt from tankers is the usual spectacular disaster that makes the headlines and causes a huge clean-up operation. The oil is less dense than water and therefore floats on the surface. This is a good thing - and a bad thing. By floating, a large area of oil sits on the surface, endangering any wildlife that gets in the way of it, and of course, it is prone to drifting and being washed ashore, where it despoils beaches and again is a hazard to all the wildlife there. On the other hand, because it floats, it is less of a hazard to life below the surface and by floating it is both obvious and available for clean-up. In such cases, there have been several approaches taken floating booms are laid around the spill to contain it and then the surface of the contained oil can be sucked up and the oil separated from the water again by virtue of its lower density and because it is immiscible i.e. does not easily mix with water. Making oil mix with water is possible by use of surface active agents (think soap-like chemicals) and these have been sprayed on spills to allow the oil to disperse. However sometimes the effects of these chemicals are as bad as the oil itself and it is found on the whole that the environment can do a pretty good job of dispersal if left alone particularly if the spill is in a stormy area. More insidiously, there are small oil spills and leakages occurring all the time, and sometimes unscrupulous deliberate discharges are made (illegally) when a ship cleans out its tanks. Anyhow, your question is an insightful one, as the relative densities of immiscible substances like oil and water are very useful properties for scientists. Often by forming two layers of liquids, a dissolved substance (called a solute) can be extracted from one solvent to another maybe into a more volatile one (easier to evaporate) and then by distillation the solute can be recovered as a pure or nearly pure substance. Its an old but effective and commonly used technique by chemists in the laboratory. I hope Ive understood your question and provided the sort of answer you were looking for. Thanks again, for asking.
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