Re: Can knowing about the density of substances solve oil spills in the ocean?

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. It’s an 
old but effective and commonly used technique by chemists in the 
laboratory.

I hope I’ve understood your question and provided the sort of answer you 
were looking for. Thanks again, for asking.