Melting Point MIT Digital Lab Techniques Manual
[MUSIC PLAYING] PROFESSOR: Throughout your laboratory experiences, you will frequently need to assess the purity or identity of a crystalline solid. Both of these goals can be accomplished by determining a compound's melting point. When a compound is in a crystalline solid state, the intermolecular forces that are holding the molecules together greatly outweigh the kinetic energy that is trying to pull them apart. Therefore the molecules appear to vibrate in a fixed location. If energy is introduced into the system in the form of heat, the kinetic energy of the molecules and thus the temperature of the system is increased. At a certain point, the molecular kinetic energy is high enough to overcome the attractive forces that are holding the molecules together. As a result, the crystal lattice breaks down and the molecules enter a liquid state. The temperature at which the solid and liquid phases of a compound are in equilibrium at a certain pressure is called the melti...