Talk:Salt and ice challenge

new german source?

An anonymous editor has added the following source : Busse, Marc-Heinrich (2013): Mutproben aus naturwissenschaftlicher Perspektive. Befunde und Interventionsansätze zu einem aktuellen Internetphänomen. Der andere Verlag. this appears to be a reference to the following paper http://neuebuecher.de/vlbid/0-4560003/ which has the english title translation of "Tests of courage from a scientific perspective. Findings and intervention approaches to a recent Internet phenomenon" Certainly this may be on topic, but the source does not appear to be backing anything as no content was added, and the source isn't in english so does not appear to add much value to the english wikipedia. My gut says its link/cite spam, but I will let others weigh in. Gaijin42 (talk) 20:38, 20 January 2014 (UTC)

freezing point

Froglich You are incorrect, they did interview a chemist. [1]Associate Professor of Chemistry at Park University, Donna Howell, said with just pure water under the conditions of a test she conducted, the water started crystallizing at point-three degrees Celsius. She said add 30 percent of salt to the water, and the freezing is well below negative 10 degrees Celsius.“So what they have in their hands, is well below negative 10 and that’s enough to give you pretty serious frostbite,” she said.Howell also said keep in mind, the kids who have tried this are putting pure salt on their arms, and not just 30 percent. Gaijin42 (talk) 17:02, 27 August 2014 (UTC)

They interviewed a chemist -- but did not have her perform an experiment whose parameters were pertinent to the challenge:

"Associate Professor of Chemistry at Park University, Donna Howell, said with just pure water under the conditions of a test she conducted, the water started crystallizing at point-three degrees Celsius. She said add 30 percent of salt to the water, and the freezing is well below negative 10 degrees Celsius."

The freezing point of LIQUID water is irrelevant in the context of a situation involving already frozen chunks of ice at 0F (-18C) pulled straight from the freezer (0F is the default freezer setting for mass-market refrigerators; meat-lockers can be considerably lower, down to -20F or -30C). Either Donna is incompetent or more likely was unaware of why a reporter was asking her questions about the freezing point of salt-water solutions (or had her commentary culled for just the juiciest sound-bite). In the salt and ice challenge, salt is poured into a mound on the skin, then an ice-cube is put into the mound. The ice-cube begins to melt (at below 32F but certainly above 0F), and the chilly brine causes frostbite -- but no more so than if the ice were applied directly. The salt is there to keep the ice cube parked instead of sliding as it melts (this is particularly the case in variants where pressure is applied). Sugar would also do the job, but dissolves slower and makes a sticky mess. (Sugar also doesn't sting when pressure-ground into a wound.)--Froglich (talk) 17:31, 27 August 2014 (UTC)

Yes, the ice starts solid - just like when making ice cream - and you add salt to that ice to dramatically lower the temperature. Body heat melts the first layer of ice, and you suddenly have liquid water mixing with salt. The Enthalpy change of solution of that mixture is endothermic lowering the temperature, and due to the lowered freezing point due to Eutectic system magic, it stays a liquid, which has a more efficient transfer of heat from the body to the water. I agree, the chemistry involved is not unique to salt, but it doesn't mean it isn't really happening. While you could get some minor skin damage from pure ice/water, the chance of severe injury is greatly increased by adding salt. Gaijin42 (talk) 17:45, 27 August 2014 (UTC)

http://butane.chem.uiuc.edu/cyerkes/Chem104ACSpring2009/Lecture_Notes_104/lect3.html goes into some detail about the chemistry/math of salt and ice specifically. Gaijin42 (talk) 15:07, 15 September 2014 (UTC)