The key difference between congruent and incongruent melting point is that congruent melting point refers to the temperature at which the melting of a solid into its liquid form occurs in a way that the composition does not change, whereas incongruent melting point refers to the temperature at which the melting of a substance occurs in a way that the composition changes.
The congruent melting point of a substance is created when it melts sharply at a constant temperature into a liquid of the same composition as that of the solid from which the liquid was created. The incongruent melting point of a substance is created when it melts to a liquid having a composition that is different from the solid substance. Congruent and incongruent melting points usually happen in two component systems.
CONTENTS
1. Overview and Key Difference
2. What is Congruent Melting Point
3. What is Incongruent Melting Point
4. Congruent vs Incongruent Melting Point in Tabular Form
5. Summary – Congruent vs Incongruent Melting Point
What is Congruent Melting Point?
The congruent melting point of a substance occurs when the substance melts sharply at a constant temperature into a liquid of the same composition as that of the solid from which the liquid was created. This type of melting occurs when a solid substance melts uniformly. An example of this type of melting is the magnesium-zinc system (Mg(Zn)2).
What is Incongruent Melting Point?
The incongruent melting point of a substance is created when a substance melts to a liquid having a composition that is different from the solid substance. This type of melting occurs when a solid substance does not melt uniformly.
An example of this type of melting is the sodium chloride-water system in which a two-component system forms different compositions upon melting (e.g. solid sodium chloride, ice, liquid mixture, sodium chloride in association with two water molecules – NaCl.2H2O).
What is the Difference Between Congruent and Incongruent Melting Point?
The congruent melting point of a substance occurs when it melts sharply at a constant temperature into a liquid of the same composition as that of the solid from which the liquid was created. Whereas, the incongruent melting point of a substance occurs when it melts to a liquid having a composition that is different from the solid substance. The key difference between congruent and incongruent melting point is that congruent melting point refers to the temperature at which the melting of a solid into its liquid form occurs in a way that the composition does not change, whereas incongruent melting point refers to the temperature at which the melting of a substance occurs in a way that the composition changes.
Moreover, the magnesium-zinc system (Mg(Zn)2) is an example of congruent melting whereas the sodium chloride-water system is an example of incongruent melting.
The below infographic presents the differences between congruent and incongruent melting point in tabular form for side by side comparison.
Summary – Congruent vs Incongruent Melting Point
Congruent and incongruent melting points usually happen in two-component systems. These are two opposing terms. The key difference between congruent and incongruent melting point is that congruent melting point refers to the temperature at which the melting of a solid into its liquid form occurs in such a way that the composition does not change, whereas incongruent melting point refers to the temperature at which the melting of a substance occurs in a way that the composition changes.