The key difference between triple point and eutectic point is that at the triple point, three phases of a substance exist in equilibrium, whereas at the eutectic point, a particular eutectic mixture freezes or melts.
Changing the temperature and pressure of a chemical system can change the physical state or phase of that system because the components in that system have particular melting and boiling points at which the phase changes take place between solid, liquid, and gas phases.
CONTENTS
1. Overview and Key Difference
2. What is Triple Point
3. What is Eutectic Point
4. Triple Point vs Eutectic Point Diagram
5. Summary – Triple Point vs Eutectic Point
What is Triple Point?
The triple point is the temperature and pressure at which solid, liquid, and vapour phases of a particular substance co-exist in equilibrium. It describes a specific thermodynamic state of matter. Sometimes, the triple point may involve more than one solid phase when there are polymorphs of the substance exist. In a phase diagram, the triple point is the point at which all three boundary lines meet with each other.
Figure 01: Triple Point
What is Eutectic Point?
Eutectic point is the temperature and pressure at which a certain liquid mixture transforms into two solid phases at the same time upon cooling the liquid. A eutectic system is a homogenous mixture of substances that can melt or solidify at a temperature that is lower than the melting point of the constituents in that mixture. Moreover, the term eutectic temperature describes the lowest possible melting temperature for all possible mixing ratios that are involved in the formation of the mixture.
Figure 02: Eutectic Point
Upon heating a eutectic mixture, the lattice of one component in the mixture will melt first at the eutectic temperature. However, upon cooling the eutectic system, each component in the mixture tends to solidify, forming the lattice of that component at a distinct temperature. Solidification happens until all materials become solids. In general, a eutectic system contains two components: thus, at eutectic temperature, the liquid transforms into two solid phases at the same time and at the same temperature. Thus, we can name this type of reaction as a three-phase reaction. This is a specific type of phase reaction; for example, a liquid solidifies, forming alpha and beta solid lattices. Here, the liquid phase and solid phase are in equilibrium with each other, a thermal equilibrium.
What is the Difference Between Triple Point and Eutectic Point?
The triple point is the temperature and pressure at which solid, liquid, and vapour phases of a particular substance co-exist in equilibrium. The term Eutectic point is the temperature and pressure at which a certain liquid mixture transforms into two solid phases at the same time upon cooling the liquid. The key difference between triple point and eutectic point is that at the triple point, three phases of a substance exist in equilibrium, whereas at the eutectic point, a particular eutectic mixture freezes or melts. In other words, at the triple point, three phases co-exist at the same temperature and pressure conditions, whereas at the eutectic point, a liquid converts into two solid phases at the same temperature and pressure conditions.
The below infographic lists the differences between triple point and eutectic point in tabular form for side by side comparison
Summary – Triple Point vs Eutectic Point
In brief, the triple point is the temperature and pressure at which solid, liquid, and vapour phases of a particular substance co-exist in equilibrium, while the eutectic point is the temperature and pressure at which a certain liquid mixture transforms into two solid phases at the same time upon cooling the liquid. The key difference between triple point and eutectic point is that at the triple point, three phases of a substance exist in equilibrium, whereas at the eutectic point, a particular eutectic mixture freezes or melts.
Reference:
1. Connor, Nick. “What Is Triple Point of Water – Definition.” Thermal Engineering, 3 June 2019.
Image Courtesy:
1. “Phase-diag2” By Matthieumarechal (CC BY-SA 3.0) via Commons Wikimedia
2. “Eutectic system phase diagram” By Eutektikum_new.svg: *Eutektikum.gif: Dr. Báder Imrederivative work: Michbich (talk)derivative work: Wizard191 (talk) – Eutektikum_new.svg (CC BY-SA 3.0) via Commons Wikimedia