<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
I received a question about what should be in these sections. I
give a short <br>
synopsis in my on-line example. There's information in the manual
and on<br>
Carmen and the Undergrad web site where you do you pre-labs. Make
sure<br>
you address the Points to Consider, at a minimum. Here's what
should<br>
essentially be in each section: <br>
<br>
Results/Discussion: <br>
<br>
In this section you will have essentially 3 paragraphs: <br>
<br>
1) Discuss what was done in a general way w/o giving
experimental details <br>
of the procedure. Don't list every little step you
did. <br>
<br>
For instance, for exp 5 (coffee-cup calorimetry exp)
you might have something like: <br>
<br>
"In this experiment a coffee-cup calorimeter was used
to determine the heats <br>
of reaction for two experiments. The heat capacity
of the coffee cup was <br>
first determined. The cup was then used to
determine the heat of reaction for <br>
a strong acid-strong base neutralization reaction and
the heat of reaction between <br>
magnesium and HCl. These heats of reaction were
used, along with those for <br>
other reactions given in the manual, to determine the
heats of reactions for two <br>
additional reactions using Hess's Law." <br>
<br>
Something along these lines should be done for each
exp. <br>
<br>
2) The most important results should be given in the 2nd
paragraph. You don't need <br>
to give every single number you obtained. You
should have a discussion of the <br>
results. Were they correct? If you can't tell,
were they at least reasonable? How <br>
do you know they were reasonable. <br>
<br>
In exp 5 (CAL) you determined heats of reaction.
Were they reasonable? Heats of <br>
reaction are on the order of 10's to 1000's of
kJ/mole. Were the ones you determined<br>
in this range. Were they positive or negative and
does it make sense? Was the heat <br>
capacity of the coffee-cup negative? The manual
told you to set it to zero if you got <br>
a negative heat capacity. Why did it tell you to do
this? What could have made it come <br>
out negative? <br>
<br>
For exp 2 (dTf) you should be discussing whether the
MW values are reasonable. <br>
Where the freezing points obtained for the different
trials reasonable (follow what<br>
would be expected with inc. solute conc.)? Does your
average MW makes sense?<br>
Would a MW of 20 amu (g/mol) make sense? How about
10,000 amu (g/mol)?<br>
Look at the "Points to Consider".<br>
<br>
If you had more than one trial how well did the
results for the trials agree. If you are <br>
taking an average of 3 or more trials and one of the
trials was very different than the <br>
others you could leave it out and just average the
others. You would discuss that <br>
in this paragraph. You technically should do an
error analysis to see if it's okay to <br>
leave out that piece of data (see the link "Treatment
of Numerical Data" at the <br>
"Laboratory" link on my web page or in Appendix F of
the manual). This should be <br>
explained here or in the next paragraph about errors.<br>
<br>
3) Errors. You need at least 2 inherent sources of error.
These are errors which are <br>
pretty much beyond your control due to the way we've
designed the exp. It doesn't <br>
mean there's no human element. These are errors
that would have affected your <br>
results. How could they affect your results? How
could they be fixed? <br>
<br>
For instance, in exp 5 (CAL) a single coffee cup was
used as the calorimeter. While<br>
it actually does a pretty decent job heat can escape
or get in, especially through the lid.<br>
Normally, one uses a double-walled Styrofoam cup
(essentially two cups together) with<br>
a special lid made of cork (which doesn't easily
allow the transmission of heat through<br>
it). Sometimes people state "the water wasn't
swirled before each temperature reading".<br>
That is NOT an inherent error. That's your error.
I've seen "a little water splashed<br>
out of the cup when the copper cylinders were dropped
in". Again, that's your error<br>
(a "do-over" error) not an inherent error. Another
inherent error in exp 5 would be <br>
some heat was lost when the Cu cylinders were
transferred from the boiling water bath <br>
to the cup. If you did this transfer quickly enough
not much would have been lost but <br>
some had to be lost no matter how quickly you
transferred the cylinders. <br>
<br>
Can you put such errors (your errors) in this
section? Yes, but you have to have at least <br>
two sources of inherent error. <br>
<br>
What else might go here? If you've left a data
point out of the best-fit line because it<br>
seemed to be way out of line with the other data
points a discussion of this being done<br>
would go here. <br>
<br>
You should always discuss how these errors may have
occurred and affected the results. <br>
<br>
<br>
<b>Remember, you need to address the Points to
Consider at a minimum</b><b>.<br>
</b><b> </b><br>
Conclusion: <br>
<br>
This is one paragraph of about 4-6 lines. I't's more or
less a summary of the Discussion.<br>
It's a one or two sentence summary of what was done
(essentially summarize the first<br>
paragraph in the Discussion section). You should have the
most important result listed<br>
again (e.g. the average of the trials). You should answer
the purpose/objectives. <br>
<br>
Remember, you shouldn't use "I" or "we". In other words, don't say
"I used a coffee-cup <br>
calorimeter...". Don't say "My results were ..." <br>
<br>
We don't accept one word answers in lab reports. You should always
have an explanation. <br>
The same generally goes for questions on quizzes. <br>
<br>
I hope this helps. <br>
<br>
Dr. Zellmer
</body>
</html>