[NetBehaviour] A DIALOGUE WITH SARAH, AGED 3...

Michael Szpakowski szpako at yahoo.com
Sat Aug 25 16:40:20 CEST 2007


:)
m.
--- marc garrett <marc.garrett at furtherfield.org>
wrote:

> A DIALOGUE WITH SARAH, AGED 3: IN WHICH IT IS SHOWN
> THAT IF YOUR DAD IS 
> A CHEMISTRY PROFESSOR, ASKING “WHY” CAN BE
> DANGEROUS.
> 
>
http://www.scribd.com/word/html_iframe/1063?guid=27zta2fh7pppm
> 
> By Stephen McNeil
> 
> - FROM THE ARCHIVES -
> 
> SARAH: Daddy, were you in the shower?
> 
> DAD: Yes, I was in the shower.
> 
> SARAH: Why?
> 
> DAD: I was dirty. The shower gets me clean.
> 
> SARAH: Why?
> 
> DAD: Why does the shower get me clean?
> 
> SARAH: Yes.
> 
> DAD: Because the water washes the dirt away when I
> use soap.
> 
> SARAH: Why?
> 
> DAD: Why do I use soap?
> 
> SARAH: Yes.
> 
> DAD: Because the soap grabs the dirt and lets the
> water wash it off.
> 
> SARAH: Why?
> 
> 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.
> 
> SARAH: Why?
> 
> DAD: Why does soap form micelles?
> 
> SARAH: Yes.
> 
> DAD: Soap molecules are long chains with a polar,
> hydrophilic head and a 
> non-polar, hydrophobic tail. Can you say
> ‘hydrophilic’?
> 
> SARAH: Aidrofawwic
> 
> DAD: And can you say ‘hydrophobic’?
> 
> SARAH: Aidrofawwic
> 
> DAD: Excellent! The word ‘hydrophobic’ means that it
> avoids water.
> 
> SARAH: Why?
> 
> DAD: Why does it mean that?
> 
> SARAH: Yes.
> 
> DAD: It’s Greek! ‘Hydro’ means water and ‘phobic’
> means ‘fear of’. 
> ‘Phobos’ is fear. So ‘hydrophobic’ means ‘afraid of
> water’.
> 
> SARAH: Like a monster?
> 
> DAD: You mean, like being afraid of a monster?
> 
> SARAH: Yes.
> 
> DAD: A scary monster, sure. If you were afraid of a
> monster, a Greek 
> person would say you were gorgophobic.
> 
> (pause)
> 
> SARAH: (rolls her eyes) I thought we were talking
> about soap.
> 
> DAD: We are talking about soap.
> 
> (longish pause)
> 
> SARAH: Why?
> 
> DAD: Why do the molecules have a hydrophilic head
> and a hydrophobic tail?
> 
> SARAH: Yes.
> 
> DAD: Because the C-O bonds in the head are highly
> polar, and the C-H 
> bonds in the tail are effectively non-polar.
> 
> SARAH: Why?
> 
> DAD: Because while carbon and hydrogen have almost
> the same 
> electronegativity, oxygen is far more
> electronegative, thereby 
> polarizing the C-O bonds.
> 
> SARAH: Why?
> 
> 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.
> 
> 
> 
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