Freezing Point of Naphthalene

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Freezing Point of Naphthalene

I.Purpose

To determine the freezing point of a known substance, naphthalene

II.Materials

ringstandgas source
test tubetest tube clamps
thermometer naphthalene
Bunsen burner goggles
hosestopwatch

III.Procedure

1.Assemble the Bunsen burner, attaching one end of the hose to the burner and the
other to a gas source.
2.Assemble the ring stand so that a ring clamp is attached to the stand holding the
test tube that will be used in the experiment.
3.Fill the test tube to approximately 1/8 capacity with
naphthalene crystals.
4. Place the thermometer in the crystals so that it is surrounded by the naphthalene
powder but not touching the sides or bottom of the test tube. Use a clamp to hold
the thermometer in place.
5. Ignite the Bunsen burner and using direct heat melt the naphthalene powder until
it completely turns to a liquid. When the temperature reaches approximately 90o
Celsius, stop heating.
6.Observe the change in temperature from 90o to 70o Celsius, recording the
temperature at regular intervals, preferably 15 seconds. This data will be used to
make a chart later.
7.Once the temperature has fallen to 70o, melt the naphthalene which is now
frozen to remove the thermometer. Properly dispose of
the naphthalene liquid as
instructed by the teacher.

IV.Data

Time ElapsedTemperature of NaphthaleneTime
Temperature

Initial (0:00)100oC7:00
78.5oC
0:3097.5oC7:15
78.3oC
1:0093.0oC7:30
78.3oC
1:3089.5oC7:45
79.0oC
2:0086.1oC8:00
79.0oC
2:3084.6oC8:15
79.0oC
2:4582.3oC8:30
79.0oC
3:0081.2oC8:45
79.0oC
3:1581.0oC9:00
79.0oC
3:3080.5oC9:15
78.5oC
3:4580.2oC9:30
78.1oC
4:0080.0oC9:45
78.0oC
4:1579.9oC10:00
78.0oC
4:3079.8oC10:15...
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