Water is one of the least understood compounds on earth. It expands when it freezes, it boils at an unusually high temperature for such a small sized molecular compound and its solid form floats in its liquid form. Other than that, water has the highest surface tension of any liquid except for mercury. It’s a shame, but the thing that covers most of the planet and two thirds of the human body is really a mystery to us. And now, we can add one more strange thing to the list: it has a second liquid state between 40 and 60 degrees Celsius.
So, scientists found out that there is a second liquid state of water. But what does that actually mean? Well, states of matter are determined by the shape, density, intermolecular distance and various other properties of compounds. So an international team from Oxford University, led by Laura Maestro, decided to look at these properties of water from 40-60 C.
They looked at thermal conductivity, refractive index, conductivity, surface tension, and the dielectric constant (which is how well electricity spreads throughout a substance at different temperatures). They found that there was a noticeable shift between 40-60C for all these properties. The crossover temperatures were:-
- 64 C for thermal conductivity
- 50 C for refractive index
- 53 C for conductivity
- 57 C for surface tension
The reason for these shifts is possibly the hydrogen bonds in water that hold the molecules together. They are constantly forming and breaking, altering the properties of water. The thing is, these bonds also exist in Ammonia, but it turns to gas at room temperature.
This new state of matter in water could have different implications for material science. As the team from Oxford puts it:
“For example, the optical properties of metallic (gold and silver) nanoparticles dispersed in water, used as nanoprobes, and the emission properties of … quantum dots, used for fluorescence bioimaging and tumour targeting, show a singular behaviour in this temperature range…[It also] raises the question of whether temperature-driven structural changes in water affect biological macromolecules in aqueous solutions, and in particular in proteins, which are the vital functional biological units in living cells.”