Density and Temperature for the Dummy Chemist

Density vs. temperature graph for water

Look back over the thousand-plus entries in this blog, and it's a safe bet that you'll find hundreds of places where we've bemoaned the scientific illiteracy of liberal arts majors attempting to freelance about STEM topics. Maybe thousands of places... In a lot of cases, we've let potential DotD candidates slide because, like the proverbial blind pig and its acorn, they've stumbled over the right answer. Sometimes, though, the journey to the answer is every bit as telling as the answer itself. That was sure what caught our eye in "How to Calculate Densities at Various Temperatures," posted to Sciencing.com by Athena Hessong.

Hessong, a history grad and sometime teacher, clearly had to reach for this science-y topic. Our geekier staffers figured out pretty quickly that the OQ (probably a high-school chemistry student) wasn't interested in temperature's effects on the density of liquids or solids – after all, at one atmosphere, the density of common liquids varies only by about half a percent between freezing and boiling temperatures. Athena, however, devoted well over half her post to liquids; including these "instructions":

1. Subtract the final temperature in degrees Celsius from the initial temperature in degrees Celsius.
2. Multiply this temperature difference by the volumetric temperature expansion coefficient for the substance being measured, and add one to this number.
3. Divide the initial density of the fluid by this number to find the final density at the new temperature.

We weren't certain which "this number" to use where. It appears that Athena needed to learn the words "product" and "sum"? Even then, we aren't really sure WTF Hessong's "answer" was supposed to be, and we couldn't find any such equation in her references. While we were looking at this, we noticed that Athena botched her example: the density of water at 30°C is lower than the density at 20°C, not higher (see graph above). That is, of course, because the relationship should be t₁-t₀,not t₀-t₁. Perhaps if she understood the principle? But no...

We also laughed at her unfamiliarity with scientific and mathematical terminology, as demonstrated by the sentence,

"Add 273.15 to the degrees in Celsius to find the degrees in Kelvin"

Really? "the degrees in Celsius"?  Couldn't she just say "temperature"? And that whole "degrees in Kelvin" thing probably makes real scientists a little queasy – most of them just say "kelvins," and are aware that the term is not capitalized.

As for Hessong, though, her science chops are pretty sparse. That's one of the reasons Crystal, err, Athena, has already collected six Dumbass of the Day awards, half of them in sciences. Congratulations, lady, on your seventh.

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