On food and cooking the science and lore of the kitchen ( PDFDrive ) 1529

for electrons than the two hydrogen atoms,
andsothesharedelectronsareheldcloserto
theoxygenthantothehydrogens.Asaresult,
there’s an overall negative charge in the
vicinityoftheoxygen,andanoverallpositive
charge around the hydrogen atoms. This
unequal distribution of charge, together with
thegeometryofthecovalentbonds,resultsin
amoleculewithapositiveendandanegative
end. Such a molecule is calledpolar because
it has two separate centers, or poles, of
charge.
A hydrogen bond results from the attraction
between oppositely charged ends of polar
molecules (or portions of molecules). This
kind of bond is important because it’s very
common in materials that contain water,
becauseitbringsdifferentkindsofmolecules
into close association, and because it’s weak
enough that these molecular associations can
changerapidlyatroomtemperature.Manyof


the chemical interactions in plant and animal
cellsoccurviahydrogenbonds.
Very Weak Bonds Between Nonpolar
Molecules: Fats and Oils A fourth kind of
chemicalbondisveryweakindeed,betweena
hundredthandaten-thousandthasstrongasa
molecule-making covalent bond. Thesevan
der Waals bonds, named after the Dutch

chemistwhofirstdescribedthem,arethekind
of flickering electrical attraction that even
nonpolar molecules can feel for each other,
thankstobrieffluctuationsintheirstructures.
Whereelectricallypolarwaterisheldtogether
as a liquid by hydrogen bonds, nonpolar fat
molecules are held together as a liquid and
given their appealingly thick consistency by
vanderWaalsbonds.Thoughthesebondsare
indeed weak, their effect can add up to a
significant force: fat molecules are long
chainsandincludedozensofcarbonatoms,so
each fat molecule can interact with many