At some point or another, we have all wished we had the Midas Touch and could turn anything we touched into gold. And although alchemy – a speculative chemical science to achieve the transmutation of base metals into gold – still eludes us, scientists may have discovered the next best thing – turning water into a shiny, golden metal!
The Magic of Water
Normal, unfiltered tap water can conduct electricity, due to salts contained within the water, meaning electrons can easily flow through the water molecules. Pure, distilled water is however the perfect insulator and cannot conduct electricity. Purified water does not contain any foreign molecules, only water molecules that are loosely linked to one another via hydrogen bonds. This means the outermost electrons of the water molecule remain bound to their designated atoms, prohibiting the movement of electrons, preventing purified water from conducting electricity.
Most materials that function as insulators are capable of becoming metallic if put under enough pressure. In theory, this process can also be done by applying enough pressure to purified water, causing the water molecules to press together. This pressure causes the valence shells (the outermost ring of electrons surrounding each atom) to overlap, allowing electrons to flow freely between each water molecule. This pressure could theoretically also turn water into what is technically defined as a conductive metal. Unfortunately, this is easier said than done, as the pressure needed to turn press the valence shells of water together and turn water into a metallic state is approximately 15 million atmospheres of pressure (about 220 million psi), which is out of reach of the current laboratory techniques and experimental capabilities. Due to this intense pressure, geophysicists believe that water-turned-metal may exist within the cores of large planets and stars in our solar systems, such as Jupiter, Neptune and Uranus.
Turning Water into Metal
An international collaboration of 15 scientists from eleven research institutions wanted to determine whether they could turn water into metal without requiring the immense pressures only found within Jupiter’s core. Last year, a team of scientists demonstrated a similar effect with ammonia. To turn water metallic, the scientists used alkali metals found in Group 1 of the periodic table, including elements like sodium and potassium, which each hold only one electron on their valence shells. When forming chemical bonds, alkali metals tend to donate this one electron to other atoms, as the loss of that electron makes the alkali metal more stable.
Although alkali metals can react explosively when mixed with pure water, scientists theorized that if the explosion could somehow be avoided, they can use the electrons from the alkali metals to turn the water into metal. So the scientist set out to do just that, and published their findings in Nature.
The challenge was to design an experimental set-up that would slow the reaction between the water and the alkali metals so that it was not explosive. Luckily, the team of scientists had a solution. For the experiment, the scientists placed a syringe filled with sodium and potassium within a vacuum chamber, and squeezed out the small liquid droplets of the metals. The sodium-potassium alloy is liquid at room temperature. In the vacuum chamber, the alkali metal droplets have a silver metallic sheen. They then exposed the metal droplets to a small amount of water vapour. To the delight of the scientists, the water condensed on the alkali metal droplets and formed a 0.000003-inch film over the metal droplets. Electrons from the metals began diffusing into the water, along with positive metallic ions. To prevent an explosion from happening, the electrons had to move faster than an explosive reaction could take place.
Once the electrons had moved from the alkali metals to the water, an incredulous event occurred: for a short moment of about 5 seconds, the water turned a shiny, golden color. As the water continued to absorb, the color gradually turned bronze for another 2-3 seconds. Eventually, the drop lost the metallic sheen and turned purple/blue and finally white, due to the formation of an alkali hydroxide layer. Using spectroscopy, the scientists were able to show that the golden yellow color was in fact the moment the water turned metallic. They documented this phase transition as BESSY II. The scientists were not sure what their study would find, and one of the co-authors of the publication said: “It was amazing, like when you discover a new element”.
The study proved that not only can water be turned to the metal on the surface of Earth, albeit in a vacuum chamber (and not inside the core of a large planet), but it also characterized the spectroscopic properties associated with the golden sheen. Spectroscopy studies the absorption and emission of light and other radiation by matter, as well as studying the interactions between particles such as electrons, protons and ions, and their interaction with other particles as a function of their collision energy. The two decisive fingerprints of a metallic phase are the plasmon frequency and the conduction band. The scientists were able to determine these two quantities using optical reflection spectroscopy and synchrotron X-ray photoelectron spectroscopy.
The scientists concluded that the metallic water solution that they formed in the vacuum chamber should be viewed as a dynamically evolving system that comprises a high concentration of excess electrons that form a conduction band. Their study demonstrated that by absorbing water vapour on sodium-potassium drops, the vigorous (and explosive) chemical reactivity can be sufficiently suppressed for visual observation, for a few seconds, and spectroscopic characterization of the formed gold-coloured layer of metallic solution, bypassing the need to use unrealistically high pressures found inside the cores of planets and stars to metalize water.
The scientists hope that their research is just the first step of water-turned-metal alchemy, and that future studies will investigate the evolution of the water vapour on the surface of the sodium-potassium drops, including the metal-to-electrolyte transition, as well as the accompanying chemical transformations.