Density for Dummies

Immiscible liquids

There's an old joke about a helicopter pilot lost in the fog who deduces that he is outside Microsoft's Redmond, Washington, offices because he receives "help" that is technically accurate but totally useless. We've seen this happen many times before, cases of dumbassery in which an eHow contributor regurgitated factoids aplenty, yet still failed to address the real question. Today's dumbass is another Demand Media/eHow freelancer writing under the pseudonym Serm Murmson. Serm addressed the topic "How to Explain Density"¹ for the Seattle PI education (I use that word loosely) blog.

While "Serm" didn't terribly misinform anyone in this article, he (she?) went off track and wandered down a rathole of sorts in his rabid desire to meet Demand Media's minimum word count. Presumably, that's why he included the following paragraph:

"You can visualize density by mixing different liquids together. In fact, oil and vinegar salad dressings offer a way to visualize density. In a mixture of oil and vinegar, the oil is less dense than the vinegar. Consequently, it floats on the top of the mixture. This is why certain salad dressings separate into layers and must be shaken before use."

Well, duh, Serm, you ol' "thinker," you. The problem was the lack of "thinking" inherent in the last sentence. Yes, vinegar has a specific gravity of 1.08 and oils (rapeseed, palm or olive) have specific gravities of 0.92-0.94, but that isn't the reason why they "separate into layers and must be shaken before use." They separate into layers because the two liquids are immiscible. Maybe if you knew jack about science you'd be familiar with the concept and the word, but apparently you don't. That's why you're today's Dumbass of the Day, Serm Murmson!

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was    education.seattlepi.com/explain-density-3893.html

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