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<big><font size="2"><big>I've received some questions about exactly
what you need to do for the<br>
first lab this week. </big></font></big>Everyone is doing
exp 1 the first week of class.<br>
<br>
<big><font size="2"><big>The TAs should cover at least some of what
I have below in lab. I<br>
addressed some of this in my previous e-mails, at least in
general.<br>
You should also look at the exp 1 help link in the "Helpful
Tidbits"<br>
link on my class web page (not Carmen). This link has several<br>
items which will help with the lab report and data analysis.<br>
</big></font></big><big><font size="2"><big><big><font size="2"><big>One
particular question I've been asked is about the data<br>
table for the notebook.<br>
<br>
</big></font></big></big></font></big><font size="2"><big>When
you look at some of the experimental write-ups in the<br>
manual you will see questions throughout the discussion and<br>
maybe even the procedure. For exp 1 you have questions<br>
on pages 3 and 4. We do not collect these. They are actually<br>
answered at the end of the write-up for the exp (page 11 for<br>
exp 1). They are supposed to be there to for you to answer<br>
so you know if you are understanding what you're reading.<br>
</big></font><br>
<font size="2"><big><font size="2"><big><font size="2"><big>In exp 1
you are using several different types of volumetric<br>
glassware. The manual states to use volumes between 5 mL<br>
and 25 mL and then instructs you to look at the figure.</big></font></big></font><font
size="2"><big><font size="2"><big><b> Use</b><b><br>
</b><b> volumes of around 5, 10, 15 and 20 (mL) for the
buret, pipet</b></big></font></big></font><br>
<font size="2"><big><font size="2"><big><b> </b></big></font></big></font><font
size="2"><big><font size="2"><big><b>and</b><b> graduated
cylinder. For the beaker use volumes of around</b><b><br>
</b><b> 20, 25, 30 and 35 (in mL).</b> <br>
</big></font></big></font></big></font><br>
<font size="2"><big><font size="2"><big><font size="2"><big>What
should be written in the notebook? There are some
things<br>
which you do before lab. Everything done in lab is
recorded<br>
directly in the notebook and nowhere else.<br>
</big></font></big></font></big></font><br>
<font size="2"><big><font size="2"><big><font size="2"><big><big><font
size="2"><big>For exp 1 you should have your
purpose, procedure and a data table in<br>
your notebook when you go to your first lab. </big></font></big><big><font
size="2"><big><big><font size="2"><big>There is no
on-line prelab.<br>
<br>
</big></font></big>The data table on the
report sheet has mass of water and volume of
water.<br>
However, in the lab you will not get the mass of
the water directly from a<br>
single measurement. This may also apply to the
volume (particularly<br>
when using a buret).<br>
<br>
You will be using a weighing beaker which you need
to weigh (just once)<br>
when it's dry. You will add water to the beaker
and reweigh it getting the<br>
total mass of the beaker and water. Thus you may
want to have another<br>
column in your data table for the total mass of
water and beaker and<br>
then a column just for the mass of the water
(which you will calculate).<br>
You may need another column for the volume of
water depending on how<br>
you do things. For the buret you may not start
your water right on zero,<br>
and even if you do, you should be recording the
initial buret reading and<br>
the final buret reading. The amount added would
be the difference<br>
between the two. If you start the water right on
0 you should record this<br>
(with the correct # of sig. fig.). Then the
amount you add can go directly<br>
into your data table as the volume of water.
However, if you don't start<br>
right on zero you will need to record the initial
and final volumes<br>
somewhere and then write the difference in your
data table for the volume<br>
of water added. You can write down some of these
numbers elsewhere in<br>
the notebook and put just the needed numbers (mass
of water and volume<br>
of water) in the data table in your notebook.
However, keep things<br>
organized so someone (besides you) could pick up
your notebook and find<br>
these numbers and understand just what you did.<br>
<br>
Please read Appendix D of the lab manual about how
to use the buret and<br>
pipet and pay attention to the number of sig.
figs. (and decimal places) which<br>
you should be recording in the notebook. Always
record your data to the<br>
correct # of s.f. and use units.<br>
<br>
You should use the analytical balance for all your
masses. While for certain<br>
pieces of glassware the top-loading balance would
suffice, if you use the<br>
analytical balance, which is more accurate and
gives more decimal places<br>
(and thus sig. fig.), you won't need to worry
whether it's safe to use the<br>
top-loading balance. Plus, then the s.f. in the
density will be due to the<br>
piece of glassware used to measure the desired
volume of water and make<br>
for a more direct comparison of the accuracy of a
particular piece of<br>
glassware.<br>
<br>
Pipets and burets are meant "to deliver", assuming
you use them correctly.<br>
<br>
Beakers are meant "to contain" the amount in the
beaker.<br>
<br>
Graduated cylinders can be tricky. Look at the
top of the graduated<br>
cylinders. There you will find either a "TD" or
"TC". You should write<br>
this down in the notebook. The "TD" means "to
deliver" while the "TC"<br>
means "to contain". This can make a difference and
you want to record<br>
this so you can discuss this in your report and
how it might affect your results.<br>
You should use the one(s) marked with "TD" when
possible for this exp.<br>
<br>
Also, while the measured density is a calculated
value you may want<br>
to do this calculation and record the numbers in
your notebook. For each<br>
piece of glassware the density you obtain for each
mass and volume should<br>
be the same. Thus, if three of them are very
close and one isn't something is<br>
wrong and you may wish to at least redo the one
which is very different than<br>
the others. Also, the density of water should be
close to 1 g/mL. If what you<br>
obtain is noticeably different you may have made a
mistake. You want to do<br>
this before putting everything away and leaving
lab.<br>
<br>
<br>
Dr. Zellmer</big></font></big><br>
</big></font></big></font> </big></font>
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