the melting and freezing points of napthalene

8/11/2019 The Melting and Freezing Points of Napthalene

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ACTIVITY 2.2


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To determine the melting and freezing pointof naphthalene, C10H8


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Boiling tube, 250 cm3 beaker, stirringthermometer, tripod stand, retort stand and

clamp, Bunsen burner, stopwatch, conicalflask, wire gauze


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Naphthalene, C10H8, tap water


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1) A boiling tube was filled with naphthalene,to a depth of 3 cm and a thermometer was

put into it.

2) The boiling tube was suspended in a beakerhalf-filled with water using a retort stand anda clamp. The level of Naphthalene in theboiling tube was ensured to be below level ofwater in the beaker


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3) The water was heated and the naphthalenewas stirred slowly with the thermometer .

When the temperature of naphthalenereached 60 C, the stopwatch started.

4) The temperature and state(s) of thenaphthalene were recorded at half-minuteinterval until the temperature of thenaphthalene reached 90 C


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Thermometer

Boiling tube

Water

Naphthalene, C10H8


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1) The boiling tube in activity A was removedfrom the water bath. The outer surface of theboiling tube was dried and immediately it wasput into a conical flask. The naphthalene ,C10H8, was stirred continuously.

The temperature and state(s) of thenaphthalene were recorded at half-minuteintervals until the temperature dropped toabout 60 C


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Time

(min)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C) 61.0 65.0 67.0 71.0 80.0 80.0 80.0 83.o 89.0

State Solid Solid Solid Solid Solidand

Liquid

Solidand

liquid

Solidand

liquid

Liquid Liquid


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Time

(min)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C) 87.0 84.0 81.0 80.0 80.0 80.0 80.0 76.0 73.0

State Liquid Liquid Liquid Liquidandsolid

Liquidandsolid

Liquidandsolid

Liquidandsolid

Solid Solid


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The flat section in each graph indicates achange of state. The temperature remains

constant as the heat energy is used to changethe state of napthalene


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1) To ensure that naphthalene is heatedevenly / naphthalene is flammable

2) a) to ensure an even cooling and minimizethe heat loss to the surrounding

b) to avoid supercooling


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3) The melting and freezing point of naphthalene

4) In the heating curve of naphthalene, the heat

energy absorbed by the particles is used toovercome the forces between the particles sothat the solid can turn into liquid.

In the cooling curve of naphthalene, the heatloss to surrounding is exactly balanced by theheat energy liberated as the particles attract oneanother to form a solid


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The melting and freezing point ofnaphthalene are the same which is __C

the melting and freezing points of napthalene

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