The key difference between sublimation and deposition is that sublimation is the change of a solid substance into a gaseous substance without going through a liquid phase whereas deposition is the change of a substance from a gas phase to a solid phase without passing the liquid state.
Phase transition refers to changing the phases of a substance. External factors like temperature and pressure changes affect this process. For instance, a liquid solidifies when we reduce the temperature to its freezing point, and it may go into the gas phase when the temperature is at its boiling point. Phase transition generally has an order; solid goes into the liquid phase and then to the gas phase; or if it is a gas, it should go through the liquid phase first and then to the solid phase. Sublimation and deposition are phase transitions, but they are a bit different than normal transitions as they do not follow this order.
CONTENTS
1. Overview and Key Difference
2. What is Sublimation
3. What is Deposition
4. Side by Side Comparison – Sublimation vs Deposition in Tabular Form
5. Summary
What is Sublimation?
Sublimation is the process of changing a solid substance into a gaseous substance without going through the liquid phase. In simple words, a solid substance directly evaporates and become a gas without being a liquid first. However, this process needs extra energy. Therefore, this is an endothermic process. By calculating the enthalpy of sublimation, we can calculate the energy needed for this process: by adding both enthalpy of fusion and enthalpy of vaporization together.
Sublimation occurs at temperatures and pressures below the triple point of the substance. For example, solid carbon dioxide sublimes at a very low temperature (-78.5°C) and at atmospheric pressure. The triple point of carbon dioxide is 5.2 atm and -56.4°C, and above this point, we can obtain liquid carbon dioxide as well. Ice and iodine can also undergo sublimation.
Figure 1: Dry Ice Sublimation
In sublimation, the chemical properties of the compound remain unaltered, but the physical properties may change. Sublimation is useful for various purposes. For example, it is used to purify chemical compounds.
What is Deposition?
Deposition is the opposite process of sublimation. It is also known as de-sublimation. Here, a substance in the gas phase changes into the solid phase without passing the intermediate liquid state.
Figure 2: Frost Formation
Unlike the previous process, this process releases energy; therefore, it is an exothermic process. Furthermore, this happens when forming ice or frost. In this process, water vapor directly goes into the solid phase (forming ice or frost). When this happens, they remove thermal energy to the external environment.
What is the Difference Between Sublimation and Deposition?
Sublimation is the opposite of deposition. The key difference between sublimation and deposition is that sublimation is the change of a solid substance into a gaseous substance without going through the liquid phase whereas deposition is the change of a substance from a gas phase to a solid phase without passing the liquid state.
Moreover, a significant difference between sublimation and deposition is that sublimation is endothermic whereas deposition is exothermic.
The below infographic provides more details on the difference between sublimation and deposition.
Summary – Sublimation vs Deposition
Sublimation is the opposite of deposition. However, both of these processes do not involve a liquid phase. The key difference between sublimation and deposition is that sublimation is changing a solid substance into a gaseous substance without going through the liquid phase whereas deposition is changing a substance from a gas phase to a solid phase without passing the liquid state.
Reference:
1. “Deposition (Phase Transition).” Wikipedia, Wikimedia Foundation, 27 Mar. 2019, Available here.
2. Helmenstine, Anne Marie, Ph.D. “Sublimation Definition (Phase Transition in Chemistry).” ThoughtCo, Jan. 13, 2019, Available here.
Image Courtesy:
1. “DryIceSublimation” By Sarathtly – Photograph taken by me (Public Domain) via Commons Wikimedia
2. “Frost patterns 4” By Schnobby – Own work (CC BY-SA 3.0) via Commons Wikimedia