Difference Between Fusion and Vaporization

The key difference between fusion and vaporization is that fusion is the conversion of a solid into a liquid, whereas vaporization is the conversion of a liquid into its vapor.

The term fusion has different definitions in different fields, but in physical chemistry, we use it to describe the process of melting. That is; fusion is the conversion of a solid phase into its liquid phase. On the other hand, conversion of a liquid into its solid is known as freezing or solidification. If the liquid phase of a substance converts into the gaseous phase, then we call it vaporization. Moreover, the energies required for each conversion are known as “heat of fusion” and “heat of vaporization”.

CONTENTS

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

What is Fusion?

Fusion is the process of melting where a solid phase turns into its liquid phase. Therefore, this term refers to a phase transition. It occurs at the melting point of the substance. The energy required for this process is called “heat of fusion”. During fusion, the entropy of the system increases because the particles that were in fixed places in the solid tends to get a chance to move in the liquid phase (this increases the randomness, increasing the entropy).

The heat of fusion or the enthalpy of fusion is the change in enthalpy. Providing heat energy to a substance to change its phase from solid phase to liquid phase at a constant pressure results in a change in enthalpy. The enthalpy of solidification is the opposite phenomena, and it has the same value for the required amount of energy. Basically,

Heat of Fusion = Heat Energy / Mass

What is Vaporization?

Vaporization is the process of conversion of a liquid phase into its vapor phase. The entropy of the system increases even more because the particles in the liquid phase gets the ability to move freely at the vapor phase. Heat of vaporization or the enthalpy of vaporization is the change in enthalpy when a liquid turns into its vapor and this is a function of pressure.

Vaporization can occur in two major ways:

Evaporation

Evaporation occurs at the surface of the liquid. It occurs at temperatures below the boiling point of the liquid at the same pressure. Moreover, it occurs only when the partial vapor pressure is less than the equilibrium vapor pressure.

Boiling

Boiling is the formation of vapor as bubbles inside the liquid. Unlike vaporization, boiling forms vapor below the surface of the liquid. It occurs when the equilibrium vapor pressure is equal to or greater than the environmental pressure.

What is the Difference Between Fusion and Vaporization?

Fusion is another term for the process of melting. Vaporization is the process of formation of vapor from a liquid, which can happen in one of the two ways: evaporation and boiling. The key difference between fusion and vaporization is that fusion is the conversion of a solid into a liquid, whereas vaporization is the conversion of a liquid into its vapor. When considering the change in enthalpy, we call the change in enthalpy during the fusion process as the heat of fusion while the change in enthalpy during vaporization is the heat of vaporization.

Summary – Fusion vs Vaporization

Fusion and vaporization are two important chemical concepts that describe two phase changes. The key difference between fusion and vaporization is that fusion is the conversion of a solid into a liquid, whereas vaporization is the conversion of a liquid into its vapor.

Reference:

1. Helmenstine, Anne Marie, “Fusion Definition (Physics and Chemistry).” ThoughtCo, Mar. 9, 2019, Available here.
2. “Enthalpy of Fusion.” Wikipedia, Wikimedia Foundation, 5 Apr. 2019, Available here.

Image Courtesy:

1. “Water Phase Change Diagram” By Cawang – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “The Water Cycle” By AIRS (CC BY 2.0) via Flickr