LATENT HEAT (CHANGE OF STATE) EXPERIMENT

TITLE: CHANGE OF STATE, LATENT HEAT.
(Determination of the melting point of a solid).

APPARATUS: 

Test tube, naphthalene, thermometer 0 – 100°C, calorimeter, stop clock, ( or watch ), ice cubes , conical flask.

DIAGRAM:

AIM: To determine the melting point of a substance.

THEORY: 

The melting point of a substance ( the temperature at which a substance melts ) is a physical property that can be used for its identification.

 It is a measure of the amount of kinetic energy (heat) that must be supplied to the particles of the substance on order to overcome the intermolecular force (such as Vander – waals, dipole – dipole and it’s bonding) that confines them to the solid state.

PROCEDURE:

1 .A boiling tube is filled with naphthalene to a depth (half full) and a thermometer is inserted into it.

2 . The boiling tube is immersed in a beaker of boiling water using a retort stand and a clamp. The level of naphthalene in the boiling tube is ensured to be below the level of water in the beaker.

3 . The boiling tube is left in the beaker until all the naphthalene has melted by stirring the naphthalene slowly with the thermometer.

4 . When the temperature of the naphthalene reaches 90°C, the boiling tube is removed from the water bath.

5 . The outer surface of the boiling tube is stirred continuously and put in a conical flask.

6 . The temperature and state (s) of yje naphthalene are recorded at half – minute intervals until all the naphthalene has solidified and the temperature drops to about 60°C.

PRECAUTION OF LATENT HEAT (CHANGE OF STATE) EXPERIMENT

1 . It was ensured that the calorimeter used was lagged properly in order to prevent heat loss to the surrounding.

2 . The experiment was conducted at room temperature in order to get accurate results.

3 . The measuring instruments were in good condition before use, 

RESULT:

The latent heat of fusion of naphthalene (melting point) is 74°C from the graph.

CONCLUSION: 

A solidifying liquid absorbs latent heat during solidification and the temperature (melting point) remains constant.