Difference Between Fusion and Solidification

The key difference between fusion and solidification is that fusion is the conversion of a solid into its liquid form. But, solidification is the conversion of a liquid into a solid.

Fusion and solidification are the processes opposite to each other. That is; fusion is turning a solid into a liquid, while solidification is turning a liquid into a solid. However, there are many other definitions for the term fusion in physics and chemistry; generally, it refers to the combination of small particles to form a bigger particle, but in comparison to the term solidification, fusion refers to a phase transition of matter, rather than combination of matter.

1. Overview and Key Difference
2. What is Fusion
3. What is Solidification
4. Side by Side Comparison – Fusion vs Solidification in Tabular Form
5. Summary

What is Fusion?

Fusion is the process of converting a solid into a liquid. And, this phase transition occurs via the melting of the solid. The process is named as such because of the term heat of fusion refers to the energy a substance requires to convert into its liquid phase at the melting point. During melting, the internal energy of the substance increases. Typically, we can facilitate the fusion of a solid by providing heat.

During this process of melting, the tight packing of ions or molecules starts to loosen. A solid substance has a well-ordered structure than a liquid. During fusion, it becomes a less ordered structure. When a solid melts, the volume increases because the liquid has no tight packing like in the solid. Therefore, density tends to decrease. But there are some exceptions as well; for example, melting of ice cubes form water. Here, the density of ice cubes is lower than water (density has increased). Therefore, ice floats on water.

Key Difference - Fusion vs Solidification

Figure 01: Fusion of Metals due to the Application of High Heat Energy

For pure crystalline solid substances, fusion takes place at a fixed temperature. And, this temperature is known as the melting point of that particular solid. The fusion of an impure substance occurs at a different temperature, not at the melting point. The temperature at which the impure substance starts to melt can vary depending on the type and the amount of the impurities present.

What is Solidification?

Solidification is the conversion of a liquid into a solid. The most common term for this process is freezing. Freezing is the conversion of a liquid state into a solid-state when the temperature is reduced below the freezing point of that liquid. In other words, it is the solidification of a liquid upon cooling. For most substances, melting point and freezing point are the same; however, there are some exceptions such as agar.

Difference Between Fusion and Solidification

Figure 02: Formation of Ice due to the Solidification of Water

Freezing often occurs in the form of crystallization. Here, crystals form from the uniform liquid. Furthermore, it is a first-order thermodynamic phase transition. That means; until the solid and the liquid coexist, the temperature of the system remains at the melting point. For example, if we consider water, water in the liquid state converts into solid-state ice upon freezing.

What is the Difference Between Fusion and Solidification?

Fusion and solidification are the processes opposite to each other. The key difference between fusion and solidification is that fusion is the conversion of a solid into its liquid form, whereas solidification is the conversion of a liquid into a solid. Further, the energy required for fusion is named heart of fusion, while the energy required for solidification is named heat of solidification.

Below infographic shows more details of the difference between fusion and solidification.

Summary – Fusion vs Solidification

Fusion and solidification are the processes opposite to each other. The key difference between fusion and solidification is that fusion is the process of conversion of a solid into its liquid form whereas solidification is the process of conversion of a liquid into a solid.

Reference:

1. Helmenstine, Anne Marie. “Fusion Definition (Physics and Chemistry).” ThoughtCo, Mar. 9, 2019, Available here.
2. Helmenstine, Anne Marie. “Solidification Definition and Examples in Chemistry.” ThoughtCo, Aug. 11, 2019, Available here.