QUIZ 2: Week of 09.03.12
Name:________________________________[7pts]
1.) Thoughtful list of 3 problem-solving strategies from last week [25 pts]
2.) Circle and label the atoms that are hydrogen bond (interactions) DONORS and ACCEPTORS in
the following molecule [18 pts] (+ 3pts for correct, - 3pts for incorrect)
I’ll talk about this in class – overlaying circles and labeling things on this image in Word is
a nightmare…
3.) Match the word to its definition bellow. THERE ARE MORE WORDS THAN DEFINITIONS
[20pts]
covalent
nucleotide
ionic
electronegativity
polar
amino acid
nucleic acid
purine
____ covalent _Referring to a stable bonding interaction between atoms; a simple covalent bond
is the result of equal or unequal sharing of an electron pair, with each atom contributing one
electron in the pair.
___ ionic __ Referring to a molecule or atom that has a negative or positive charge due to a gain or
loss of electrons.
__ electronegativity _An atomic property reflecting the “desire” or “covetousness” of atoms for
electrons (both their own and those of others). Comparison of this property allows one to predict
whether two atoms will share electrons equally, unequally, or one will lose and the other gain
the electrons altogether.
_ nucleotide _The ready-to-install state of a unit of DNA or RNA; it contains the base (the
“identity” part), a sugar (formally a “ribose”) and a string of phosphates.
_ polar Having an unequal distribution of charge, such as an O–H bond wherein the oxygen is
partially negatively charged and the hydrogen partially positively charged.
4.) Explain WHY “oil and water don’t mix”. [30 pts]
 Your answer should incorporate the concept of electronegativity
 Write it as if I (Emily) don’t understand anything, i.e. define/explain all technical
terms/jargon
Oil and water do not mix because they have fundamentally different characteristics.
Water is a polar molecule, meaning that it has a region that is partially positively charged
and a region that is partially negatively charged. This is due to the fact that O is more
electronegative (has more of a ‘desire’ for electrons) than H. Because O ends up ‘spending
more time’ with the electrons that make up the covalent bond between the O and the H, it
has a partial negative charge, whereas the H has a partial positive charge.
Conversely, oil is made up predominantly of Carbons and Hydrogens. Carbon and
Hydrogen have roughly equal electronegativities, which mean they share the electrons
that make up the covalent bond between them equally, so there is no unevenness of
charge on the oil molecule and it ends up being neutral or non-charged (greasy).
A polar (molecule with partial (+) and partial (-) regions) water molecule would ‘rather’
interact with another polar water molecule than with the non-polar/uncharged oil
molecule, so the oil molecules are ‘corralled’ into one spot because this enables more of
the water molecules to interact with other water molecules as opposed to water having to
interact with oil molecules.