Oil and water do not mix? Scientists managed to convince them

Every child knows that oil and water do not mix. Oil molecules repel water. In fact, some of the best woodworking finishes are various oils, because they protect wood from moisture. However, as always everything depends on circumstances. Scientists from The University of Edinburgh have managed to make oil dissolve in water. They say that there are some practical applications for this.

Oil floats on water, typically collecting in bid droplets Image credit: Victor Blacus via Wikimedia

In some places oil and water may mix – at the bottom of the ocean of maybe in Uranus and Neptune. The key is pressure – squeezing molecules together may make them stick. Scientists applied pressure to containers filled with water and methane to gain insights into how the chemicals interact. Of course, you may know that methane is not technically oil, but it does repel water like oil so it is commonly used in researches like that.

Hydrophobic molecules are fascinating. People spray their shoes and clothing with special substances to make them waterproof. This study shows that mixing hydrophobic molecules with water is not impossible if pressure is extremely high. Scientists compressed water and methane molecules together between two ultra-sharp diamonds. Pressure reached up to 20,000 Bars – 20 times greater than the pressure at the bottom of the Mariana trench. Scientists were predicting that something has to happen and it seems like they managed to mix methane with water.

Under normal conditions methane molecule floats on water. Methane collects into large droplets that simply do not mix with water and, looking through the microscope, it reminds oil. At extremely high pressure these droplets disappear, which means that they dissolved into water. How does this happen?

Scientists say that methane molecules shrink under pressure. Because water is not a compressible fluid, its molecules remain largely the same. And so methane manages to get in between water molecules and two substances mix together. While it may not seem like it, there are actually some useful applications for this discovery.

Industrial solvents are extremely toxic and dangerous. Mixing oil into water could help replacing these solvents with a new generation materials. Furthermore, this study could lead to insights about conditions on the ocean floor and in such planets as Uranus and Neptune. This could also help modelling planetary bodies like Saturn’s largest moon, Titan.


Source: The University of Edinburgh

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