MELTING
In this experiment, we saw some examples of soldi materials on the metal
plate which were ice, butter, wax, table salt, menthol and vanillin. We set them
on a tripod under which there was Bunsen burner.Experiment was quite
simple. We turned the burner on and observed which one melted first. Of
course, to make accurate observation we needed to take same amount of each
substance.
The melting points of the substances are as follows:
m.p. of ice = 0°C
m.p. of butter = 32°C
m.p. of menthol = 36°C - 45°C
m.p. of wax = 55°C – 65°C
m.p. of vanillin = 80°C
m.p. of table salt = 800°C
(two different datas are those of isomers of another crystal forms.)
Therefore, the order of melting is from top to bottom in the list.
Melting is the phase change from solid state to liquid state.
Melting1 (sometimes called fusion) is a physical process that results in the
phase change of a substance from a solid to a liquid. The internal energy of a
solid substance is increased, typically by the application of heat or pressure,
resulting in a rise of its temperature to the melting point, at which the rigid
1
http://en.wikipedia.org/wiki/Melting
ordering of molecular entities in the solid breaks down to a less-ordered
state and the solid liquefies. An object that has melted completely is molten.
The melting point of a solid2 is the temperature at which the vapor pressure
of the solid and the liquid are equal. At the melting point the solid and liquid
phase exist in equilibrium.
As the points that became clear after the experiment;
 We understood the difference of intermolecular forces and molecular
interaction. During the melting process, intermolecular forces between
any two particles don’t change. However, since we are heating and the
kinetic energy is increasing, distance between them increases a little. So,
molecular interaction is weakened but intermolecular forces remain teh
same. Actually, the force any two molecules never changes.
 Since the amount of energy given by the bunsen burner wasn’t enough
to break the bonds of table salt whose melting point is extremely high
compared to others, 800°C. Therefore, salt didn’t melt during the
experiment.
 Melting is a property relevant to intermolecular forces.
 Particles of solids have regular arrangement, liquids and gases have
random arrangement.
In conclusion, in this experiment, we learnt the melting process in submacroscopic level. Temperature is increasing, so does the kinetic energy which
means particles begin to move faster. Also, the force of attraction doesn’t
change but the interaction is weakened due to increased distance between the
particles.
2
http://en.wikipedia.org/wiki/Melting_point