prequizzes and answer keys

[robert zellmer]

The answer keys to the prequizzes as well as blank prequizzes are posted to
my class website ("Quizzes" link).

If you didn't take this quiz because you have a Monday recitation or missed
this week's recitation, I would suggest you print out one or more of the 
quizzes
and take it in the the allotted time and then grade yourself.  This will 
help you
determine what you might not remember.

The quizzes were not identical so everyone might want to at least look 
at quizzes
from days other than when you have recitation.  Remember as well, the 
quizzes
do not cover everything you need to remember from 1210.

One thing we noticed is quite a few people had trouble with shapes and 
polarity
of molecules.  You need to be able to tell pretty quickly if a substance 
is ionic,
molecular, metallic or covalent network.  If it's molecular you need to 
determine
quickly it's shape and polarity.  This is important in order for you 
determine
attractive forces.  There's a link at my "Notes" link which has a link 
about the
four different types of solids and the attractive forces between the 
particles.

Another problem we noticed is several people had trouble with relating 
the sign
of something like delta(H) to whether a process is exothermic or 
endothermic.
Remember, when the system loses energy to the surroundings that is a 
negative
energy change so q, delta(H), delta(E) are negative and the process is 
exothermic.
If energy is absorbed by the system the process is endothermic and the 
sign of
q or delta(H) is positive.

     delta(H) = -10 kJ/mol    the process is exothermic, energy is 
released and can
                                            be treated as a product.

     delta(H) = +10 kJ/mol    the process is endothermic, energy is 
absorbed and can
                                             be treated as a reactant.

Dr. Zellmer