Lab Report Exemplar
Research Question: What is the melting and cooling point of stearic acid?
Data Collection and Processing
Table 1: Recording the state of change of stearic acid by measuring the temperature in degrees
Celsius over six minutes
Time
Temp
(sec)
(°C)
±0.05
0.00
30
1.00
39
135
47
3.00
52*
4.00
55
* Started to melt
** Completely melted
5.00
6.00
0.00
1.00
135
3.00
4.00
5.00
58**
70
30
39
47
52*
55
58**
6.00
0.00
1.00
135
3.00
4.00
5.00
6.00
70
30
39
47
52*
55
58**
70
Table 2: Qualitative observations of stearic acid during the experiment
Observations of stearic acid
Observations of stearic acid
Observations of stearic acid
before the experiment
while melting
when melted
(50-73 seconds)
(after 73 seconds)
 Solid
 Solid with cracks
 Colourless
 Opaque
 Parts are translucent
 All liquid
 Whitish yellow colour
 Liquid is colourless
 Odourless
 Granular
 Some liquid
 Transparent
 Odourless
 Bubbling liquid
Figure 1: A graph showing the temperature change of stearic acid when it changes from solid to
liquid
Graph needs axis labels with units, proper scale, data points, title, figure title underneath
Conclusion:
In this investigation, the melting point of stearic acid was determined by heating solid stearic acid in
a water bath using a Bunsen burner. Particles in solids have a repeating arrangement with strong
intermolecular bonds holding them together (Ryan 11). Because of these bonds, the particles do
not have freedom to move freely but can vibrate (Munn, 13 Sep. 2011). The process of melting is an
endothermic reaction in which energy is added to a reaction. The Bunsen burner flame was the
energy source in this experiment. Increasing energy increases the movement of particles, which will
break bonds between solid particles (Ryan 11). As this occurs, the intermolecular bonds break,
separating solid particles and changing their state to liquid, which have greater motion (Munn,
13.Sep. 2011). Temperature should remain constant from the beginning of melting until all solid
stearic acid has changed phase to a liquid (Hyperphysics). In this experiment, stearic acid started
melting at 52°C and was completely melted by 70°C (Table 1). This range in melting point is
illustrated on Graph 1. According to research, the actual melting point of stearic acid is 69°C
(Inchem). There is no plateau region shown on graph 1 because the temperature did not remain
completely constant during the entire change of state. Temperature was not controlled perfectly,
and reasons for this will be discussed in the evaluation.
Evaluation:
Sources of Error
It was difficult to read the thermometer due to
the condensation present on the test tube from
the Bunsen burner heat.
There was no specific mass of stearic acid
measured for this experiment.
Only one trial was done for this experiment.
Could not control the amount of heat entering
the reaction using a Bunsen burner.
Temperature recording was not taken on the
minute each minute.
Solutions/Modifications
Use an electronic thermometer that records
temperature digitally, or logs data on the
computer.
Measure 5g of stearic acid using an electronic
balance to make it possible for comparisons
between group/class data.
Repeat experiment 2 more times to obtain
results for 3 trials in order to properly analyze
data.
Use a hot plate to maintain a set temperature
for the heat.
Have one partner count down the 5 seconds
before the temperature reading is to be taken so
other partner is prepared. Use data logging
equipment that records and graphs data on the
computer.
Note: I wasn’t paying attention, I did not wear proper safety goggles, I didn’t stop the stopwatch at
the correct time are not valid sources of error since YOU have control over those things.
Bibliography:
(MLA format – alphabetical order, single space between lines, double space between sources, all
lines after the first are indented)
Munn, Sharon. “Chemistry Review.” Science 10. Dubai American Academy. Dubai. 13 Sep. 2011.
Powerpoint.
“Phase Changes.” Hyperphysics. n.d. Web. 4 Oct. 2011.
˂ http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html ˃.
Ryan, Lawrie. Chemistry for You. Cheltenham: Nelson Thornes, 2001. Print.
“Stearic Acid Melting Point” Inchem. n.d. Web. 4 Oct. 2011.
˂http://www.inchem.org/documents/icsc/icsc/eics0568.htm˃.