What is the melting point?

We explain what the melting point is and what its characteristics are. Examples of melting point. Also, what is the boil.

1. What is the melting point?

It is called the degree of temperature at which solid matter melts , that is, it passes into the liquid state . This occurs at a constant temperature and is an intensive property of matter , which means that it does not depend on its mass or size: the temperature to be reached will always be the same.

The pure substances have melting points higher and lower range of variation, unlike impure substances (mixtures): the more mixed this matter, the lower the melting position and the greater the variation, up to the eutectic point , temperature corresponding to each atom of the matter in question. Thus, this property can be used, together with the boiling point of matter, to determine the purity of the materials.

The melting point, in addition, is little affected by pressure , unlike the boiling point, and is usually equal to the freezing point of matter (at which liquids become solid) for most substances .

In some cases the melting point will have negative temperature values: this means that from that temperature a frozen substance will return to its initial liquid phase.

The fusion, therefore, is a phase change process (solid to liquid) that operates from the introduction of caloric energy to the system or substance, thus making the atoms move more vigorously and overcome the rigid structure And flow.

It is a very common process in the metallurgical industry , for example, where minerals and metals are melted to give them a specific shape before allowing them to regain their strength (by cooling and losing the heat introduced).

2. Melting Point Examples

Some examples of melting points are as follows:

• Melting point of water (H ₂ O): 0 ° C
• Copper (Cu): 1085 ° C
• Aluminum (Al): 660 ° C
• Gold (Au): 1064 ° C
• Silver (Ag): 962 ° C
• Steel: around 1375 ° C (depending on its alloy)
• Carbon (C): 3500 ° C
• Potassium (K): 64 ° C
• Tungsten (W): 3422 ° C
• Argon (Ar): -189 ° C
• Ice: 0 ° C
• Alcohol: -117 ° C
• Iron (Fe): 1539 ° C
• Lead (Pb): 328 ° C
• Mercury (Hg): -39 ° C
• Nitrogen (N): -218 ° C
• Hydrogen (H): -259 ° C
• Acetaldehyde: -123.5 ° C

3. Boiling point

Similar to the melting point, the boiling point is that temperature at which the molecules of a liquid overcome their structure and undertake the gaseous form. This is what happens, for example, when boiling water and transforming it into steam . This temperature is strongly influenced by the pressure, the molecular mass of the substance and the type of intermolecular forces to overcome (polarity, covalence, etc.).

However, the boiling point cannot be increased to infinity . The critical temperature is eventually reached, above which there is no identifiable liquid phase, since the density of the gas phase increases according to the pressure. Thus, each material will present its boiling point, according to the nature and behavior of its molecules.

The melting point and boiling point are not comparable and should not be confused.