Wednesday, January 2, 2013

At least they call water a chemical

"Organic" sea salt (is it chemical-free?)
Credit goes to Drew for discovering
this on Amazon.
Chemophobia is an acknowledged problem with the general public and mass media, as evidenced by chemical-free chemistry sets, the famed and oft-repeated dihydrogen monoxide hoax, labeling of myriad products as 'chemical-free', confusing regulations about chemistry students being barred from working with any chemicals due to safety, and general ignorant wincing from major media outlets at anything that might have "um" in the name.

The public doesn't like chemicals, even if they don't know what they are.

So when in my news feed appeared an article referencing a "chemical game of chicken,"* I was quite surprised to see that the chemicals in question were salt and water (how interesting, given that Caribou Coffee, for instance, touts water as the chief ingredient in its 'chemical-free' decaffeination).

So what is this game of chicken? It's one of those hyped-up articles that come out a couple times a year to the effect of "look what stupid thing all teenagers are doing! HOW CAN YOU PROTECT YOUR TEENAGER?" (e.g. vodka eyeballing).

This round of media hype stems from Detroit; the idea is that teenagers are putting a layer of salt and a layer of ice on their skin. From HuffingtonPost:
Detroit doctors report that some area teens are partaking in dangerous trend: a "chemical game of chicken" that can result in permanent damage to their bodies. 
In the game, which is called the "salt and ice challenge," teens burn their skin by applying ice to a layer of salt on their skin and holding it for as long as possible. 
CBS News reported that adding salt can drop the freezing point of ice as low as 0 degrees Fahrenheit, resulting in severe injuries to the skin, including frostbite.
So teenagers are hurting themselves, but let's get to the real issue here: how are reporters covering the science behind the phenomenon? Let's look.

What does CBS News say about it? From their coverage:
The challenge is so painful because of the chemical processes involved. Typically water freezes at 32 degrees Fahrenheit, but adding salt causes the freezing point to drop as low as 0 degrees. When applying ice, energy is pulled from what's nearby - in this case, heat from a kid's skin. While "competitors" fight the urge to drop the ice, they risk further damage in the form of blisters or second-degree burns, or frostbite.
The science is a little off here; I don't know why 0 degrees was chosen as the arbitrary low point, since a typical ice/salt bath can achieve -20 degrees Celsius (-4 degrees Fahrenheit). It depends on amounts and how cold the ice itself is. Maybe that's just nitpicky, though.

What gets me is the third sentence: "When applying ice, energy is pulled from what's nearby - in this case, heat from a kid's skin." The sentence itself reads pretty awkwardly. But it also makes it sound like putting the ice on the salt causes the salt (or the ice) to pull heat away. In reality, as mentioned before, the salt has two functions: (1) it lowers the freezing point of water and (2) lowers the temperature of the water by endothermic dissolution.

Point (1) is crucial. The ice itself is cold (below the freezing temperature, most likely). But it's cold water that is more dangerous, since heat transfer is more efficient between a surface and a fluid than between two surfaces (that's why we use oil baths to heat reactions, and why we put water in ice baths at all).

A Fox article from Kansas City has some fun quotes. For instance:
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.
Here the reporters simply butchered the concept of concentration, which is something the public doesn't understand (see the abundant use of "pure" as a marketing term for chemically impure items). If the kids were putting "pure salt" on their arms, that'd be pretty safe, because there'd be no water/ice.

There's a treasure trove in this article from Detroit, however: The opening line from a Detroit-area news network's coverage is particularly horrifying (yes, the comma is in the original):
You know what salt does to ice on a snowy road, It causes a chemical reaction.
No... it doesn't. Dissolution is a physical change, not a chemical change; it's certainly not a chemical reaction. Simply put, physical changes can be reversed by physical means (that's the case here; the water could be evaporated off to give the salt again in its original form).

The carnage continues:
When you combine salt and ice on skin, it does damage to living cells and tissue.
Again, this isn't strictly true. Heat transfer does the damage. This requires sufficient salt/ice and a certain amount of time; it's not that salt and ice pop together and give off a red-brown death gas that begins eating skin. The same effects can occur from any coolants, really.

But my favorite line is this (I've put the entire thing in bold):
Because salt and ice are common every day items, they can't be legislated under lock and key, they can't be hidden away, there is no black market for them.
I love that the writer of the article elevates salt and ice to the level of guns, smallpox, or methamphetamine, as if our first response to reading that a couple teenagers had made a YouTube video would be to write to our Congresspeople, demanding that our voices be heard until sodium chloride and solid dihydrogen monoxide were regulated. I have visions of a salt black market in which perspiration would be evaporated and sold, giving a new meaning to sweatshops. And bans on freezers; only licensed institutes (closely watched, of course) would be trusted with the task of making and using ice (also known as solid water or frozen condensed steam).

Those dangerous chemicals.

* By "chemical game of chicken" we usually mean grad school.


  1. Great dissection of this "ice-salt chicken" practice. I'd guess alcohol ingestion is also involved. (Making them more susceptible to the horrible effects of the dreaded ice and salt?) The sweatshop analogy made me laugh out loud. Nice job!

  2. Some decades ago, I remember a fiscal inspector visiting the University of Milan and asking, shocked "but, so, here you have illegal undeclared distillation devices!" (Cannot transcribe the answer of the red-blooded director of Organic Chem Dep.)

  3. I can't decide if the public misunderstanding of chemicals is hilarious, sad, or perhaps a bit of both.

  4. Science fact: Farenheit was developed such that "100" was human body temperature and "0" was cold seawater (brine). Quite arbitrary, but most things are in US metrics. Also, quite inaccurate, considering actual human temperature is closer to 97 and cold brine (as you point out) can get as low as -4. The author of the CBS article probably chose "0" as the "historical" lower limit.

  5. This just reminded me...

    The special "pet safe" ice melt that I got from the store. On the label:
    Line 1: Contains no salt.
    Line 2: Magnesium chloride pellets.


  6. I've actually done this. No alcohol involved, just college kids being stupid. The pain happened pretty fast and I had a weird scar thing on my hand for like 2 weeks.

  7. The real ice cube risk is slipping on the damned half melted things, but I'll leave that for The Clumsy Physicist blog.


    A lot of the "anti-chemical" reaction is a product of the 70s. Chemical measurement got a lot better then, and it turned out that a lot of chemicals people assumed were safe were not quite as safe as assumed. Tetra-ethyl lead was not something one could eat safely by the spoonful as was supposedly done during the big lobbying effort backing it. DDT wasn't doing anything good for the bird population, and it wasn't doing enough harm to the mosquito population once resistance developed. Benzene processed decaf coffee wasn't as dangerous as a Tang screwdriver - 200 proof lab alcohol and Tang - but benzene was never on the list of "good for you" nutrients. Neither breathing nitrous oxide nor drinking the residues from tanning leather were particularly healthy either.

    Yes, a lot of the anti-chemical hysteria is laughable, and a lot of it is worrisome, but a lot of it flowed from a rejection of an overly confident and trusting attitude towards a broad range of chemicals now considered harmful.

  8. Very interesting post about a very contradictory topic! People today pay more attention to products they consume and especially chemicals added. Water, being vital for life, is a great example. Great insights! Thank you!