Water can also float on oil, say scientists

Can water float on oil? Yes, says a new study defying conventional wisdom which researchers say could have important applications in cleaning up oil spills that often endanger seashores and fisheries.

Normally what determines whether something floats or not is its density. For instance, hot-air balloons float because hot air is less dense than cooler air. Similarly crude oil has a lower density than seawater, which makes it to float.

But, a team at at the Curtin University in Australia now found that conventional wisdom can be wrong by making water float on oil, LiveScience reported. The key behind the counterintuitive results involves how tightly the molecules in a liquid stick to one another as opposed to something else.

The strength of this force between molecules determines the liquid’s surface tension — how likely it resists an external force. Insects such as water striders can walk on water by taking advantage of this surface tension.

In their study, the scientists added tiny amounts of water to drops of various types of oil.

These water droplets could float on the oil, depending on how large they were and the type of oil that was used.

Commercial vegetable oil has enough surface tension to support the droplets; in contrast, pure mineral oils such as hexane, octane and decane do not.