In the heating of
naphthalene, the heat energy absorbed by the particles is used to overcome the
forces between the particles so that the solid can turn into liquid. In the
cooling curve of naphthalene, the heat loss to the surroundings is exactly
balanced by the heat energy liberated as the particles attract one another to
form a solid. That is why the temperature remains constant for sometime in both heating and cooling curves. The melting and freezing points of naphthalene, C10H8
are 80⁰C.
- Melting point: the temperature at which a solid changes into a liquid at a particular pressure.
- Freezing point: the temperature at which a liquid changes into a solid at a particular pressure.