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<div class="moz-cite-prefix">On 9/5/20 12:33 PM, wrote:<br>
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Dear Dr. Pounds, </div>
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I have been working on the lab report, and I am a tad confused.
There is a chart for exact volume and the masses from the lab,
but it says that those numbers should not be what we measured. I
am a little confused as to what they are and how I am to find
them from the measured mass and such, as I thought what we
measured is what we were supposed to use to find density.
However, it says that none of those values should be what we
found in table 1 of the lab. Why would we not use the masses and
volumes that we measured in the lab?</div>
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Thank you for your time,</div>
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<p><br>
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<p>So let's see if I can clarify this -- because I didn't write
those procedures. In the lab you recorded the initial volume in
the buret. Let's imaging that was 0.38 ml. The procedure then
tells you to place approximately 1.00 ml of water in the beaker.
That means your next buret reading should have been close to 1.38
-- but after watching students for years, I can bet that it wasn't
exactly 1.38. For the sake of this example, we'll say that it was
1.41. <br>
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<p>Similarly, your initial beaker mass might have been something
like 55.33 grams on the to loading balance and 55.3632 on the
analytical balance. After your added approximately 1.00 ml it
might have been something like 56.38 grams on the top loading and
56.4231 grams on the analytical balance<br>
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<p><br>
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<p>Those are all values that you measured. The actual volume of
water for the "~1 ml" case would be 1.41-0.38 = 1.03 ml. The
mass of the drop of water from the top loading balance would be
56.38 - 55.33 = 1.05 grams and from the analytical balance it
would be 56.4231 - 55.3632 = 1.0599 grams.</p>
<p><br>
</p>
<p>The density of water from the top loading balance would then be
1.05 g / 1.03 ml = 1.02 g/ml</p>
<p><br>
</p>
<p>The density of water from the analytical balance would be 1.0599
g / 1.03 ml = 1.03 g/ml</p>
<p><br>
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<p>So the first line of the table on the report form would be have,
using my fictional data, the entries, 1.03 ml, 1.05 g, 1.02
g/ml, 1.0599 g, and 1.03 g/ml respectively.</p>
<p><br>
</p>
<p>Note -- none of those values were found in your original Table 1
of the lab procedures because they were all calculated from those
data. Does that help?</p>
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<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a class="moz-txt-link-abbreviated" href="mailto:pounds_aj@mercer.edu">pounds_aj@mercer.edu</a>)
Professor of Chemistry and Computer Science
Director of the Computational Science Program
Mercer University, Macon, GA 31207 (478) 301-5627
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