Freezing point of Napthalene

Essay by Johnathan BeardsleyF, January 1996

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Freezing Point of Naphthalene

I. Purpose

To determine the freezing point of a known substance, naphthalene

II. Materials

ringstand gas source

test tube test tube clamps

thermometer naphthalene

Bunsen burner goggles

hose stopwatch

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 Elapsed Temperature of Naphthalene Time Temperature

Initial (0:00) 100oC 7:00 78.5oC

0:30 97.5oC 7:15 78.3oC

1:00 93.0oC 7:30 78.3oC

1:30 89.5oC 7:45 79.0oC

2:00 86.1oC 8:00 79.0oC

2:30 84.6oC 8:15 79.0oC

2:45 82.3oC 8:30 79.0oC

3:00 81.2oC 8:45 79.0oC

3:15 81.0oC 9:00 79.0oC

3:30 80.5oC 9:15 78.5oC

3:45 80.2oC 9:30 78.1oC

4:00 80.0oC 9:45 78.0oC

4:15 79.9oC 10:00 78.0oC

4:30 79.8oC 10:15 77.5oC

4:45 79.4oC 10:30 77.0oC

5:00 79.1oC 10:45 76.5oC

5:15 79.1oC 11:00 76.0oC

5:30 79.0oC...