-1=e^ipi Posted January 30, 2015 Report Posted January 30, 2015 (edited) Been following this a while. Nice to see that it's finally going to be published in nature. It's a good example that shows how the conventional wisdom in science can be wrong for hundreds of years and all it takes is for someone to just buy some basic materials online, explode them in front of a camera, and then wonder why it is concurring in order for the conventional wisdom to be falsified. Edited January 30, 2015 by -1=e^ipi Quote
Bonam Posted January 30, 2015 Report Posted January 30, 2015 (edited) Is there a summary article? Edited January 30, 2015 by Bonam Quote
-1=e^ipi Posted January 30, 2015 Author Report Posted January 30, 2015 Is there a summary article? The video doesn't summarize? Basically, a new type of 'explosion' has been discovered (in this case for alkali metals in water). The traditional explanation for the past 100+ years is that the alkali reacts with the water along the surface of interaction, creating and Alkali hydroxide and hydrogen. Unfortunately, the traditional explanation greatly fails to explain the speed of the reaction and why it is an 'explosion'. The new explanation is that along the surface of the interaction, valence electrons are transferred from the alkali metal to the water. This causes a bunch of positively charged alkali ions to be right next to each other and a bunch of negatively charged water ions to be right next to each other. Since like charges are repulsed, the alkali metal and water along the surface starts to expand in the direction perpendicular to the surface of interaction, which creates new surface of interaction for the process to repeat (more electrons get transferred and further electric repulsion). The overall effect is that you get these explosions that occur on very small timescales. Quote
jacee Posted January 30, 2015 Report Posted January 30, 2015 And what's a practical application of that? Quote
TimG Posted January 30, 2015 Report Posted January 30, 2015 And what's a practical application of that?Explosions due to these reactions are a common problem in foundries and many workers have been killed over the years. This new understanding allowed them to propose using a small amount of soap in the water to inhibit the reaction. Initial tests show this approach is effective and will help prevent a common type of industrial accident. Quote
-1=e^ipi Posted January 30, 2015 Author Report Posted January 30, 2015 (edited) And what's a practical application of that? This sounds like what William Gladstone asked Michael Faraday on his experiments in electromagnetism. To quote Faraday, "Why sir, there is every probability that you will soon be able to tax it". But with respect to this Coloumbic explosion, the main practical benefit will probably be for workers that deal with molten metal (ex. people that work in a smelter/foundry); for example, they found that adding 5 g of hexanol to a litre of water completely suppressed this explosion. Beyond that, I don't really know. It would probably be too impractical/expensive for a weapon. But scientific discovery doesn't need a practical application, extending human knowledge has its own value. It is not every day that people find new physical mechanisms like this. Edited January 30, 2015 by -1=e^ipi Quote
Bonam Posted January 30, 2015 Report Posted January 30, 2015 The video doesn't summarize? Basically, a new type of 'explosion' has been discovered (in this case for alkali metals in water). The traditional explanation for the past 100+ years is that the alkali reacts with the water along the surface of interaction, creating and Alkali hydroxide and hydrogen. Unfortunately, the traditional explanation greatly fails to explain the speed of the reaction and why it is an 'explosion'. The new explanation is that along the surface of the interaction, valence electrons are transferred from the alkali metal to the water. This causes a bunch of positively charged alkali ions to be right next to each other and a bunch of negatively charged water ions to be right next to each other. Since like charges are repulsed, the alkali metal and water along the surface starts to expand in the direction perpendicular to the surface of interaction, which creates new surface of interaction for the process to repeat (more electrons get transferred and further electric repulsion). The overall effect is that you get these explosions that occur on very small timescales. Thanks for the summary. I like my science in text form Found the paper: http://www.nature.com/articles/nchem.2161.epdf?referrer_access_token=sPl2vC6PDhJlQH8TtMraaNRgN0jAjWel9jnR3ZoTv0PivizcYhbeEeedGtf_JDb9_jGU2Nb3sPLqPi0hS5MQCIR06CK_vNaGX2y0sGG7yS6iWJFKndp6y7JSxl55kN-1 Quote
TimG Posted January 30, 2015 Report Posted January 30, 2015 (edited) Thanks for the summary. I like my science in text form Found the paper:The proliferation of videos without any associated text is a pet peeve of mine. I can scan text very quickly to get a summary - videos require a much higher time investment to get summary information. Edited January 30, 2015 by TimG Quote
-1=e^ipi Posted January 30, 2015 Author Report Posted January 30, 2015 (edited) Decided to do some basic calculations. Density of sodium is about 0.97 g/cm3. Atomic mass of sodium is 23 g/mol. Sodium metal has a cubic lattice. On can calculate the distance between adjacent sodium nuclei from this. A cubic cm of sodium weights 0.97 g so has 0.97/23 mols, or ~ 2.54 x 1022 atoms. The cube root of this is 2.94 x 107 atoms, which are how many atoms you have across and edge of the cube. Divide this by the length of the cube and you get 3.40 x 10^-10 m, which is the distance between adjacent sodium nuclei. Now if you consider two sodium ions separated by 3.40 x 10^-10 m, the coulombic repulsion between these two ions is 8.988 x 109 Nm2C-2 * (1.6022 x 10-19 C)2/(3.40 x 10-10 m)2 = 1.996 x 10-9 N. Given the mass of the sodium atom (~ 23 * 1.675 x 10-27 kg), this means that the acceleration of a sodium ion is on the order of 5.18 x 1016 m/s2. That is very fast. Edited January 30, 2015 by -1=e^ipi Quote
Bonam Posted January 30, 2015 Report Posted January 30, 2015 (edited) Decided to do some basic calculations. Density of sodium is about 0.97 g/cm3. Atomic mass of sodium is 23 g/mol. Sodium metal has a cubic lattice. On can calculate the distance between adjacent sodium nuclei from this. A cubic cm of sodium weights 0.97 g so has 0.97/23 mols, or ~ 2.54 x 1022 atoms. The cube root of this is 2.94 x 107 atoms, which are how many atoms you have across and edge of the cube. Divide this by the length of the cube and you get 3.40 x 10^-10 m, which is the distance between adjacent sodium nuclei. Now if you consider two sodium ions separated by 3.40 x 10^-10 m, the coulombic repulsion between these two ions is 8.988 x 109 Nm2C-2 * (1.6022 x 10-19 C)2/(3.40 x 10-10 m)2 = 1.996 x 10-9 N. Given the mass of the sodium atom (~ 23 * 1.675 x 10-27 kg), this means that the acceleration of a sodium ion is on the order of 5.18 x 1016 m/s2. That is very fast. Atomic spacing of a few angstroms is typical for most solids. The acceleration seems "very fast"...but these kinds of very high (and much higher) accelerations are encountered very commonly in chemistry and physics on these scales. The thing to remember is that acceleration doesn't happen for very long. In some sense, the acceleration in this sense is less meaningful anyway since particles do not move classically but according to the rules of quantum mechanics on these scales. But yes, it is this electrostatic repulsive force which results in the Coulomb explosion. The really interesting part of the phenomenon (to me at least) is the rapid metal spike formation through the Rayleigh instability. It is cool that new discoveries about commonly observed processes like this remain to be made. Edited January 30, 2015 by Bonam Quote
Bonam Posted January 30, 2015 Report Posted January 30, 2015 The proliferation of videos without any associated text is a pet peeve of mine. I can scan text very quickly to get a summary - videos require a much higher time investment to get summary information. Agreed. A 25 min video is a considerable time investment... I can read a summary article with similar information content in 2-3 minutes, and in 25 minutes I read the entire paper. Quote
GostHacked Posted January 31, 2015 Report Posted January 31, 2015 Agreed. A 25 min video is a considerable time investment... I can read a summary article with similar information content in 2-3 minutes, and in 25 minutes I read the entire paper. Don't worry the Superbowl will take your whole afternoon. Quote
Bonam Posted February 1, 2015 Report Posted February 1, 2015 Don't worry the Superbowl will take your whole afternoon. Not a football fan. I'll be out in the delightfully empty mountains while the superbowl is going. Quote
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