Sarah, aged 3, Learns About Soap | The Curious Cat Science and Engineering blog explores: innovation, technology, research, education, economics, gadgets, health care and scientific inquiry.

A Dialogue with Sarah, aged 3: in which it is shown that if your dad is a chemistry professor, asking “why” can be dangerous [the broken link was removed] by Stephen McNeil.

DAD: Why does the soap grab the dirt?
SARAH: Yes.
DAD: Because soap is a surfactant.
SARAH: Why?
DAD: Why is soap a surfactant?
SARAH: Yes.
DAD: That is an EXCELLENT question. Soap is a surfactant because it forms water-soluble micelles that trap the otherwise insoluble dirt and oil particles.

Great. I remember such discussions with Dad (Chemical Engineering professor). The only danger I saw was him getting tied of -why? (when I was older). And sometimes giving me answers the teacher didn’t like (a way of doing math problems that wasn’t the way my teacher was teaching).

DAD: Why is oxygen more electronegative than carbon and hydrogen?

SARAH: Yes.

DAD: That’s complicated. There are different answers to that question, depending on whether you’re talking about the Pauling or Mulliken electronegativity scales. The Pauling scale is based on homo- versus heteronuclear bond strength differences, while the Mulliken scale is based on the atomic properties of electron affinity and ionization energy. But it really all comes down to effective nuclear charge. The valence electrons in an oxygen atom have a lower energy than those of a carbon atom, and electrons shared between them are held more tightly to the oxygen, because electrons in an oxygen atom experience a greater nuclear charge and therefore a stronger attraction to the atomic nucleus! Cool, huh?

(pause)

SARAH: I don’t get it.

DAD: That’s OK. Neither do most of my students.

Related: Why Use Designed Factorial Experiments? – “I said, but you explained that to me and I am just a kid, how can you be teaching adults that? Didn’t they learn it in school?”

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