New study reveals water's 'split personality'

Wednesday, June 18, 2014, 5:57 PM - Scientists at Princeton University have used a computer model to examine water as it freezes and in the process, they've discovered it has a 'split' personality -- dividing into separate liquid forms when exposed to certain temperatures and pressure thresholds.

At cold temperatures the molecules in most liquids slow down, eventually creating a solid substance that will sink if placed in more liquid.

Ice, on the other hand, behaves differently and floats.

That's because water molecules push away from each other as they get colder -- creating low density regions i.e., areas with fewer molecules in a given space, mixed with higher-density regions.

As temperatures plunge further the low-density regions win out, resulting in solid ice that's less dense than the water it came from.

Researchers created a virtual world to examine how water behaves in extreme conditions. The molecules began to split into two liquids of different densities at temperatures around -45C and at about 2,400 times normal atmospheric pressure.

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"Our results suggest that at low enough temperatures water can coexist as two different liquid phases of different densities," said study contributor Pablo Debenedetti in a statement.

Researchers say the two forms "coexist a bit like oil and vinegar in salad dressing".

"Some of the molecules want to go into one phase and some of them want to go into the other phase," adds study contributor Jeremy Palmer.

Researchers say the discovery that water has a "dual" nature could shed new light on how it behaves in high-altitude clouds before falling to the Earth as hail or snow.

Debenedetti says a better understanding of water may also help improve weather and climate forecasting models.

The complete paper can be found in the journal Nature.