Difference Between Sublimation and Heat Transfer

The key difference between sublimation and heat transfer is that sublimation is a change in the state of matter whereas heat transfer is a change in the state of energy.

Sublimation and heat transfer are two topics that we discuss under energy and state of matter. These concepts are very important in the study of fields such as thermodynamics, matter transition, power generation, and power transfer, and in almost every mechanical system. Thus, a clear understanding of these concepts is important in order to excel in the above fields.

CONTENTS

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

What is Sublimation?

Sublimation is the process of changing the state of the matter directly from solid to a gas without going through a liquid phase. Usually, when we heat up a solid to its melting point, it will change its phase to a liquid. When the liquid is further heated up to its boiling point, it will change the state to a gas. This is not the case with sublimation. Sublimation is the process of directly changing the state from solid to gas.

We can observe this process only under special situations in special materials. Pure naphthalene is such a subliming material. Another substance that sublimes is solid carbon dioxide, which is also known as dry ice. Iodine crystals, ice, and snow behave as subliming material under some conditions. The misty gas evolving from an ice cube is subliming ice.

What is Heat Transfer?

We must first understand the concept of heat in order to understand the concept of heat transfer. Thermal energy, or heat, is a form of internal energy of a system. Thermal energy is the reason for the temperature of a system. It occurs due to the random movements of the molecules of the system. Every system that has a temperature above absolute zero has positive thermal energy. The atoms themselves do not contain any thermal energy. But, atoms have kinetic energies. When these atoms collide with each other and the walls of the system, they release thermal energy as photons. Heating such a system will increase the thermal energy of the system. Higher the thermal energy of the system, higher the randomness of the system.

The above image shows the four major methods of heat transfer: evaporation, conduction, convection, radiation. Heat transfer is the movement of heat from one place to another. When two systems, which are thermally contacted, are in different temperatures, heat from the object at the higher temperature will flow to the object with a lower temperature until the temperatures are equal. A temperature gradient is necessary for a spontaneous heat transfer. We measure the rate of heat transfer in watt whereas the amount of heat is measured in joule. The unit watt equals “joules per unit time”.

What is the Difference Between Sublimation and Heat Transfer?

Sublimation is the process of changing the state of the matter directly from a solid to a gas without going through a liquid phase. Heat transfer is the movement of heat from one place to another. The key difference between sublimation and heat transfer is that sublimation is a change in the state of matter, whereas heat transfer is a change in the state of energy. Apart from that, heat can be converted to other forms of energy and then be transferred, but in sublimation, no such change is possible. Moreover, sublimation is also a heat transfer from the solid state of matter to the gas state of matter.

Below is the comparative summary of the difference between sublimation and heat transfer.

Summary – Sublimation vs Heat Transfer

Sublimation is directly related to heat transfer because it involves the transfer of the heat of a substance transfers from one phase to another phase of matter. The key difference between sublimation and heat transfer is that sublimation is a change of the state of matter whereas heat transfer is a change of state of energy.

Reference:

1. María Dolores Luque de Castro, José Luis Luque García, in Techniques and Instrumentation in Analytical Chemistry, 2002.
2. Helmenstine, Anne Marie, Ph.D. “Sublimation Definition (Phase Transition in Chemistry).” ThoughtCo, Jan. 13, 2019, Available here.

Image Courtesy:

1. “Dry Ice Sublimation 1” By Christopher from Salem, OR, USA – Fun with Dry Ice 1Uploaded by Diaa_abdelmoneim (CC BY-SA 2.0) via Commons Wikimedia
2. “Heat Transfer” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia