High-speed cameras help explain high-school chemistry
Nature Chemistry
January 27, 2015
The initial mechanism of the explosion that occurs when alkali metals, such as sodium or potassium, are dissolved in water is described in Nature Chemistry this week.
Dropping alkali metals into water is frequently used to wow high-school chemistry classes. Students are taught that, once triggered, the vigorous explosion is caused by heat release, steam formation and the ignition of the hydrogen gas that is produced. Whilst true, the trigger, and why the initial formation of steam and hydrogen gas does not simply deactivate the surface reaction before an explosion can occur, has not previously been well understood.
Pavel Jungwirth and colleagues used high-speed cameras and simulations to study the explosive reaction. Their data suggests that the explosive behaviour is triggered by an almost immediate release of electrons from the metal, which leaves behind positively charged metal atoms that strongly repel each other. This leads to the rapid protrusion of metal spikes from the surface, which increases the surface area over which the subsequent metal-water reaction can occur, explaining the propagation of the reaction.
doi: 10.1038/nchem.2161
Research highlights
-
Jun 30
Evolution: Hawks learn on the fly to swoop up before perchingNature
-
Jun 28
Astronomy: Hydrogen- and helium-rich exoplanets may provide habitable conditions for billions of yearsNature Astronomy
-
Jun 24
Sport science: New wearable sensor to measure neck strain may detect potential concussionScientific Reports
-
Jun 23
Scientific community: Women credited less than men in scientific paper authorshipNature
-
Jun 22
Planetary science: Modelling electrolyte transport in water-rich exoplanetsNature Communications
-
Jun 15
Robotics: Taking millimetre-scale origami robots for a spinNature Communications