CHM 1412 UNT Crystallization of Sodium Acetate Lab Report

Grading Rubric for NLC CHEM Lab ReportsLab Report Sheet
The following is a breakdown of the different parts of the Lab Report for all labs except
Experimental Design. The Experimental Design lab has a slightly different format as outlined in
the next section.
1. Performing the lab and recording data: ~60 points (may vary). There may also be some
pertinent calculations.
2. Questions and problems: ~ 20 points (may vary). These will be at the end of the Report
Sheet. Show your work.
3. Conclusion: 20 points. Not all North Lake labs require a written conclusion, this varies
from course to course. Currently only CHEM 1407 and CHEM 1412 online are required to
write conclusions for every lab. The 20 points for the conclusion replaces the 20 points lab
quiz. The Experimental Design Lab does not have a quiz and for this lab, everyone has to
write a conclusion (see breakdown for Experimental Design Lab below). The conclusion
should be succinct and NOT a reiteration of the procedure. It should have the following:
 Thesis statement or Explanation of the Lab – one sentence that explains what the
lab’s purpose is.
 Results and Conclusion – experimental data and analysis to either support or
disprove the thesis.
 Error Analysis
Please see the rubric below for further details on the conclusion.
Lab Report Sheet – Experimental Design
The following is a breakdown of the different parts of the Experimental Design Lab Report.
1. Unknown identification/answering the specific question – 10 pts
There may be calculations that will be checked for accuracy.
2. Procedure – 20 points
Must write a step by step procedure that anyone can follow and get consistent,
reproducible results. Make sure that the procedure is clear and unambiguous. This
necessitates attention to detail, do not leave out any steps. Do NOT copy and paste a
procedure from one of your labs or from other sources (this is plagiarism). Put it in your
own words.
3. Conclusion – 20 points. See rubric below.
4. Case Study – 25 points
Read the case study and answer the question posed. Document your position from
credible sources.
 10 pts- thesis statement
 10 pts – argument
 5 pts – citations/bibliography
5. Team Work 25 pts – Please answer the questions honestly. There is no right or wrong
answer. No points will be deducted unless you do not answer the question. We are
interested in your experience with your team. For the online Experimental Design Lab
you will reflect on a previous team experience you have had. You do not need to work in
a team for the experiment.
Rubric for Conclusions
The table below is a guide to what is expected of a conclusion and how it will be graded. Be
aware of the distinctions between “Observations” and “Results.”*
 Observations are descriptions of what you perceive with your senses. That is, what
you see, hear, or smell (but not taste or feel since we abide by safety regulations and
do not permit direct contact with chemicals in our labs!). For example if you mix two
solutions and a solid forms, you can describe that you saw a solid materialize from
the solutions which were previously liquid. You could write something like “a solid
formed from two liquids.” The more descriptive, the better. Was there a color
change? Do not merely say “it was orange” since perhaps the liquid started out an
orange color. Say rather “the solution changed from green to orange.” Or “an orange
solid formed from two clear liquids.” The more detailed, the better.
Do NOT write the formula of the solid (even if you know it) under “Observations.”
One obviously cannot “observe” the formula of a compound! (Figuring out the
formula of the solid would be a “result” or “conclusion.”)
 Results is the presentation of the data and observations. They may be a calculation
of the data or a deduction from observations. For example the result is that a
precipitation reaction occurred since you observed a solid appearing in the solution.
A result could be your suggestion of the formula of the precipitate. The formula of
the precipitate would NEVER be an observation since we can’t see the atoms or
molecules. But it could be a result that you suggest from your observations and
knowledge of the solutions you mixed together. Results could also include what was
learned from the experiment on an individual level and may include applications you
see to the world around us. For example you could say “I had no idea that dissolving
salt in water changes its physical property of freezing point! Now I understand why
they “salt” the roads in icy weather.” There should be enough detail for someone not
familiar with the lab to understand what was done and what was learned. The Result
section should also include an error analysis. (You can put an error analysis in a
separate paragraph if you prefer.) See rubric for conclusions below for details on what
is included in an error analysis. The last sentence of this part should be your
conclusion which is a summary of what the lab proved.
*Scientific Research Journal papers also include a Discussion section. We will not deal with
this since we are not doing original research. But just so you know, the Discussion section is
where you analyze your results and explain their meanings. The Discussion will include any new
questions (and possible answers) and perspectives and describe the most interesting points for
the entire field. The Discussion section is where researchers can be wildly speculative and talk
about what they think the far reaching implications are of their research.
Conclusion Part
Expectation to receive full credit
Explanation of Lab
4 points
This is a well written sentence of the purpose or goals of the
experiment. It should be the first sentence of your conclusion.
For the Experimental Design lab your explanation will depend on the
question/problem you are given. (Length is one sentence to one paragraph)
Results and
Conclusion
6 points
Talk about what happened in the experiment. Did what happen support
or not support your expectations?
Results are not a restatement of facts and theory or a reiteration of the
procedure. DO NOT include steps of the procedure in this section.
The results are your interpretation of your observations and data. The
last sentence of this part should be a conclusion sentence. This is a
summary of what the lab proved. For our lab reports it should only be
one sentence. (Length one to three paragraphs.)
Error Analysis
6 points
Discuss any possible errors that may have occurred in your experiment.
Error analysis will first be of the technical errors that may have
happened as you performed the lab. Did you notice anything wrong
while performing the lab? Any spilling? Overheating? Generally
when performing labs you should write down observations at each step.
That way, if an unexpected result occurs you can go back and jog your
memory and perhaps figure out what error caused the unexpected
result. This section should be detailed and not general. Do NOT say
“human error caused bad results.”
Discuss the possible effects the error would have on the results. For
example if the error was that “the salt solution spattered out of the
beaker when drying” say that “since this error occurred I expect a
lower yield of salt. Therefore my percent composition of salt in the
mixture is probably lower than the actual.”
You could also include how the error could be reduced. Perhaps better
equipment? Or more care when boiling solutions?
General statements of “human error” or “calculation mistakes” are not
acceptable. (Length one paragraph.)
Spelling,
Punctuation and
Grammar
4 points
Conclusions should be free of errors in spelling, punctuation or
grammar. One point deduction for each error up to 4 points.
Examples of acceptable conclusions from NLC students:
These are conclusions that have the elements per the rubric, but some are not particularly well
written. This is a Chem class and we do not grade for literacy, only comprehensibility.
Conclusion #1
The purpose of this experiment was to become more familiar with the separation of
mixtures of solids.
I was given a mixture of sodium chloride, benzoic acid, silicon dioxide, and iron. The
mixture contained an unknown amount of each substance. I was required to separate
each substance one at a time, and then find their mass and percent of the whole
mixture. The experiment took a few days to complete because a few of the steps
required water to evaporate, leaving behind the desired substance.
Iron was the first and easiest to separate out because of its magnetic characteristics.
Next, was the sand. Since sand is insoluble in water, I put the remaining mixture in
water and put it over a fire. The Sand settled at the bottom of the beaker, and the
remaining mixture dissolved into the water. I put the liquid mixture into an ice bath. The
benzoic acid crystallized, which allowed me to filter it out, leaving behind the sodium
chloride.
The experiment required patience and close attention to detail.
Sources of Error
The errors occurred in the recovery of the mixture. I started with 5.8 grams of the
mixture and finished with 5.4 grams, which is about 93%. The results were also skewed
by the balance, and the fact that it only measures to a tenth of a gram. I lost part of the
mixture along each step, but the major loss occurred with the sand in the beaker. I
baked the sand in the oven to expedite the drying process, but some sand baked to the
bottom and the sides of the container. I dislodged most of the sand, but I lost part.
[Editor’s note: It would have been better to add a part about how it would be expected
that this would cause the sand component results to be less.]
Conclusion #2
The lab involved burning a few household items and measuring the amount of heat
released so that caloric information could be calculated. By burning the food and
measuring the heat released into the water, we are able to make the needed
calculations.
The possible errors in this lab include measuring the temperature wrong, or making the
calculations incorrectly. The second error which has been discussed before in previous
labs can be corrected by making sure to read the thermometer at eye level immediately
after removing it from the liquid. The third error is making calculations incorrectly. This
lab involved a lot of calculation which makes keeping up with Sig Figs and rounding
difficult. I tried my best to reduce my errors and I thoroughly enjoyed this lab.
Conclusion #3
The purpose of this lab was to study and identify some physical and chemical properties
of gases that are commonly used in the laboratory and to use these properties to
identify these gases when there is a gas present. By combining certain chemicals,
elements, and household products, I was able to discover the different properties that
were produced and create exciting reactions. It was amazing to see the gas released
by putting the water filled pipet tubes over the stoppers with plastic gas delivery tubes.
The best part of the experiment was to see the immediate bubbling from adding
Hydrochloric Acid to the mossy zinc and the overflow of bubbling by adding two
common household items, the vinegar and the baking soda. It was also interesting to
see the color change of the BTB to a yellow color indicating an acid when the gas from
the reaction of the sodium bicarbonate and vinegar had taken place and been released
into the BTB. Any error in this lab could have been attributed to mistakes with the
pipets and releasing too much liquid or potentially mishandling and contaminating the
various chemicals that I was using because there were many different combinations
going on and some of them were messy. It was difficult to see a reaction with the
limewater at first, but as I continued to use it, I noticed the bubbling. This lab proved
very useful in becoming familiar with working with different chemicals the gas releasing
or delivery equipment. It was something I had never used before and found very
interesting.
Conclusion #4
The objective of this lab was to identify metallic ions in solutions. I soaked cotton swabs
with different salt solutions over passed them over the burner to excite the electrons of
the metals in the salts. I observed and recorded the color of the flame produced by the
excited electrons.
I was able to notice the color for each solution that was tested.
The lab experiment was very straightforward and I experienced no major complication
other than the smell produced by the occasional roasted cotton swab. The only difficult
color to identify was the calcium nitrate.
Overall, the experiments were well planned and easy to perform. I was able to complete
the lab in a minimal amount of time. I found the experiment to be interesting and
enjoyed the different colors that were produced. After completing the lab, I wondered if
more colors can be produced by mixing the metallic ions.