Answer key for version #1
Which remarks are true about hydrophobic (uncharged) vs. polar (partially charged)
things?
A = true; B = false
!
1. Water beads up on wax paper because water molecules are strongly attracted
to the wax surface
CORRECT: F or B
!
2. A water stream bends towards a static-y balloon whereas a stream of oil is unaffected
CORRECT: T or A
!
3. Oil beads up on aluminum foil because of the strong attraction of hydrophobic
molecules for each other
CORRECT: F or B
Consider the case of cotton (made from plant material derived from sugars; rich in C-O
and OH groups) vs. polyester (a synthetic material whose components are mainly carbon and hydrogen). Which remarks are true about their ability to attract water and to
dry?
A = true; B = false
!
4. The cotton would dry more slowly because water would form hydrogen interactions with it readily
CORRECT: T or A
!
5. The cotton would dry more quickly because its partial negative charges would
repel oxygen and its partial positive charges would repel hydrogen
CORRECT: F or B
!
6. The polyester would dry more slowly because 'opposites attract'
CORRECT: F or B
!
7. The polyester would dry more quickly because its carbons and hydrogens
would not offer interactions to the oxygen and hydrogens of water
CORRECT: T or A
For each question, choose the appropriate color
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A = red
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B = blue
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C = yellow
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D = gray
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E = white
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8. negative charge
CORRECT: A
!
9. carbon atom
CORRECT: D
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10. hydrogen atom
CORRECT: E
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11. oxygen atom
CORRECT: A
!
12. positive charge
CORRECT: B
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13. nitrogen atom
CORRECT: B
In a biological (WATER) environment (such as all the cases that have been discussed in
lecture and the textbook), match the description/information below to the most appropriate selection from the following:
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A = covalent bond
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B = hydrophobic exclusion
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C = ionic interaction
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D = hydrogen interaction
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E = none of the above
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14. generally involves a hydrogen and an electronegative atom on different
molecules or different parts of molecules
CORRECT: D
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15. clustering of uncharged molecules because water molecules are 'busy' interacting with each other
CORRECT: B
!
16. Interactions between two water molecules are an example
CORRECT: D
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17. An interaction between separate atoms or molecules that are charged
CORRECT: C
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18. An interaction that features a partial positive charge on a hydrogen as a central feature
CORRECT: D
!
19. Electron SHARING in order to complete outer shells
CORRECT: A
<<<<<< IMAGE: struct1.jpg >>>>>>>>>>
For the structure shown, assign partial charges as follows:
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A = partial (
!
)
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B = partial (-)
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C = neutral/no significant partial charge
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20. Oxygen #1
CORRECT: B
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21. Hydrogen #2
CORRECT: A
!
22. Carbon #3
CORRECT: C
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23. Nitrogen #4
CORRECT: B
!
24. Hydrogen #5
CORRECT: C
Match the organelle to its properties or function. Some may be used multiple times;
some none.
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A = mitochondrion
!
B = nucleus
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C= lysosome
!
D = rough endoplasmic reticulum
!
E = none
!
25. extracts sugar's energy and re-formulates it into ATP
CORRECT: A
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26. is covered with ribosomes
CORRECT: D
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27. derived from a prokaryotic cell long ago
CORRECT: A
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28. contains its own circular DNA
CORRECT: A
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29. organelle whose function corresponds to your stomach
CORRECT: C
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30. holds the genetic information
CORRECT: B
In both the actual 'discovery' of the periodic table and the in-class characterization of
liquids based on densities and properties, numbers and behaviors came together to
play a key role. Which remarks are true
A = true; B = false
!
31. They gave rise to the ability to make specific predictions about properties of
as-yet unfound elements/liquids
CORRECT: T or A
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32. They lead to the ability to discern repeating relationships is the data
CORRECT: T or A
!
33. They lead to the ability to predict properties (such as smells) that had never
been observed
CORRECT: F or B
34. Which represents the most completely correct statement about electronegativities
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A} oxygen and nitrogen have relatively large electronegativities; hydrogen and
carbon are similar to each other and have lesser values
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B} their electronegativities are all similar
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C} carbon is the most electronegative, oxygen and nitrogen are in the middle,
and hydrogen least electronegative
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D} nitrogen is the most electronegative, carbon and oxygen are the same as
each other, and hydrogen is the least electronegative
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E} carbon and hydrogen are very electronegative; oxygen and hydrogen less so
CORRECT: A
Within a given row, elements toward the right of the periodic table have ______ compared to those on the left. Pay attention! Exactly backwards is still wrong ;)
A = true; B = false
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35. a tendency to from fewer covalent bonds (considering only the rightmost 4
columns)
CORRECT: T or A
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36. more electrons in their outer shell
CORRECT: T or A
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37. a stronger tendency to take electrons to complete their outer shells
CORRECT: T or A
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38. a greater likelihood to donate electrons and become positively charged
CORRECT: F or B
39. Which of the following is the primary reason for considering eukaryotic cells better
than prokaryotic ones in general?
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A} They are more efficient because they lack nuclei
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B} They have unique capabilities in terms of chemical reactions they can perform
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C} They aren't better
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D} Some can thrive in extreme environments
CORRECT: C
The following questions are very short answer. Partial sentences are fine. Use the
blanks on the back of the the coversheet. One sentence should suffice, so target
your answer specifically to the individual question. Read all before answering so you
don’t put info in one that will be asked by the next. Points lost for irrelevant or wordy
presentation. Label each partial answer (40a, 40b, etc.). You may orient the sheet
any way you wish.
40]! Surface tension (1-sentence sequenced answers)
! a) How do the electronegativities of oxygen and hydrogen differ?
Oxygen has a significantly GREATE electronegativity than hydrogen does
! b) What is the 'bond' between oxygen and hydrogen in a water molecule made of?
A shared pair of electrons
! c) For the oxygen atom in a water molecule, what quantity of electrons does it 'own'
compared to elemental oxygen (i.e. an oxygen atom not bonded to anything) [i.e.
same, a fraction more, an extra one, fewer, etc.)
The sharing of the pair is unequal, so oxygen ends up ‘owning’ more electrons than it
started with
! d) How are partial charges distributed in a water molecule?
The oxygen ends up partially negative; each hydrogen partially positive
!
e) How do the individual properties of water molecules above give rise to surface
tension?
The partial positives on each water can interact with partial negatives on others, generating a huge, massively interlinked ‘pulling’ network
! f) How do the properties above cause water to evaporate more slowly than (for example) ethanol?
Because each water is ‘held’ by others, it takes a lot of force to ‘kick one out’. Ethanol
has fewer linkages and fewer linked part, so evaporation reflects size more accurately
41]!Oil and water (1-sentence sequenced answers)
a) How do the electronegativity of carbon and hydrogen compare?
They are similar; we’re treating them as the same
b) When carbon and hydrogen are sharing electrons, how are shared electrons distributed?
Essentially equally, such that when partnered each ‘owns’ as many as it does as an
element
c) What partial charges are present for covalently bonded carbon and hydrogen atoms (i.e. in a C-H bond)?
There are no significant partial charges present
d) Why does the charge distribution in molecules rich in C and H give rise to noninteraction with water?
There is nothing in C-H for water’s partial (+) and (-) charges to interact WITH.