Name _____________________
Due date ___________________
Assn Number ______
Melting Point Lab
You will be given an unknown substance. Your job will be to determine
its melting point, and then to identify the unknown substance using the
melting point.
For this lab, you will record your initial thoughts and data in your
science journal, but will type a formal lab report (you knew this had to
be coming sometime!)
Background knowledge (complete this in your lab report):
1. Why are we using a crystalline solid and not an amorphous solid
for this lab?
2. The melting point will help you identify the unknown substance.
What do we call a property that helps us to identify a substance,
no matter what the quantity is?
Purpose:
Complete this in your lab report.
Materials:
bunsen burner
test tube
thermometer
wire gauze
cold water
matches
goggles
ring
ring stand
two 150 mL beakers
one scoop of unknown
Procedure:
1. Set up your ring stand, ring, gauze, and burner as instructed.
2. Fill the 150 mL beaker halfway with water and place on the gauze.
3. Light the burner.
4. Place the test tube of unknown substance into the beaker. Do not
let go of it.
5. Place the thermometer into the test tube. Do not let go of it.
6. Allow the substance to heat until it melts completely. You may
gently swirl the test tube to help it along.
7. Record the melting point when you reach it.
8. Submerge the bottom of the test tube in the beaker of cold
water. Keep it there until the substance freezes.
9. Repeat steps 3-8 until you have done 3-5 trials.
10.After the final trial, melt the substance again, and pour it into
the waste container provided by your teacher.
11.Share your data with the class.
(For the report, you do not have to retype the procedure, but you
should draw a detailed, labeled sketch of the setup)
Data (include all 3 parts below in your lab report):
1. Construct a table in your science journal that will allow you to
record the melting point found in each of 5 trials.
2. With the class data, create a histogram by hand.
3. Find the mean, median, mode, and range of the data. Show your
work and display your results in a table.
Discussion and Conclusions (complete in lab report):
1. Were there any outliers in the data? Explain.
2. Based on the mean, what is the identity of this substance? Why?
3. Based on the mode, what is the identity of this substance? Why?
4. Based on the median, what is the identity of this substance?
Why?
5. How is the range helpful in analyzing your data?
6. Which measure of central tendency is the best to determine the
identity of the substance? Why?
7. Explain what happened to the molecules during this experiment.
Include a description of why the melting happened so quickly.
8. Explain why we did not need to mass the substance in each
person’s tube.
Lab Report Checklist:
_____
Title, your name (underlined), your partner’s name
_____
Background knowledge
_____
Purpose
_____
Materials (list those you actually used)
_____
Procedure (detailed, labeled sketch)
_____
_____
_____
_____
_____
_____
Data:
Data Table #1: Melting points found in 5 trials
Graph #1: Histogram of class data
Math Work #1: Calculations of mean, median, mode, and
range
Data Table #2: Measures of central tendency for class
data
Discussion and Conclusions
All work typed (graphics in pen) and spellchecked.
Melting Points of Various Substances (C)
Acetic acid
Acetylferrocene
Benzaldehyde, 2-nitro
Benzene, paradichloro
Benzil
Benzophenone
Butter
Cyclohexanol
Demethyl sulfoxide
Glutaric acid
Hexane-1,6-diamino
Ibuprofen
Napthalene
Peroxybenzoic acid, 3-chloro
Stearic acid
Vanillin
16.6
83
43.7
53.2
95.5
46
33
25.1
18.4
98
41.5
76
80.5
93
69.6
81.5