Melting Point Definition in Chemistry

Melting Point vs Freezing Point

Melting icicles
At the melting point of water, both water and ice can exist. Pixabay

The melting point of a substance is the temperature at which a solid and liquid phase may coexist in equilibrium and the temperature at which matter changes from solid to liquid form. The term applies to pure liquids and solutions. Melting point depends on pressure, so it should be specified. Typically, tables of melting points are for standard pressure, such as 100 kPa or 1 atmosphere. Melting point may also be called the liquefaction point.

Melting Point vs Freezing Point

The temperature at which a liquid changes to a solid (the reverse of melting) is the freezing point or crystallization point. The freezing point and the melting point do not necessarily occur at the same temperature. This is because some substances (e.g., water) experience supercooling, so they may freeze at a temperature much lower than they melt. So, while melting point is a characteristic property of a substance, the freezing point is not.

Sources

  • Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 1439855110.
  • Ramsay, J. A. (1949). "A new method of freezing-point determination for small quantities." J. Exp. Biol. 26 (1): 57–64.