Sublimation is an endothermic process. It requires the absorption of heat energy from the surroundings for a substance to transition directly from a solid to a gas phase, bypassing the liquid phase. 1 This absorption of heat energy is necessary to break the intermolecular forces holding the solid structure together and enable the transition to a gaseous state.
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Key Takeaways: Is Sublimation Endothermic or Exothermic?
- Sublimation is an endothermic process that requires the absorption of heat energy.
- Heat energy is needed to break the intermolecular forces and increase the kinetic energy of the particles.
- Sublimation absorbs heat from the surroundings, resulting in a cooling effect and a decrease in temperature.
Why is sublimation an endothermic process?
Sublimation is an endothermic process because it requires the absorption of energy in the form of heat in order to occur. Endothermic processes are those that absorb heat from their surroundings, while exothermic processes release heat to their surroundings. 2
During sublimation, a substance transitions directly from the solid phase to the gaseous phase without passing through the liquid phase. 3 This process requires the breaking of intermolecular forces or bonds within the solid, which requires an input of energy. 4
The energy is needed to overcome the forces of attraction between the particles in the solid and convert them into a gaseous state.
By providing heat energy to the solid substance, the thermal energy increases the kinetic energy of the particles, allowing them to overcome the intermolecular forces that hold them together in the solid phase.
As a result, the particles become more energetic and move freely as a gas. This absorption of heat energy from the surroundings causes the process to be endothermic.
It’s important to note that not all phase changes involve the same energy transfer. For example, the melting of a solid to a liquid or the evaporation of a liquid to a gas are also endothermic processes because they require the input of energy.
In contrast, processes like condensation (gas to liquid) and freezing (liquid to solid) are exothermic processes as they release heat energy to the surroundings.
Why is sublimation not an exothermic process?
Sublimation is not an exothermic process because it does not release heat to the surroundings. Instead, it requires the absorption of heat energy in order to break the intermolecular forces and convert a solid directly into a gas.
In sublimation, the solid molecules gain enough energy to overcome the attractive forces holding them together and transform into a gas. This requires an input of heat energy to break the intermolecular bonds and increase the kinetic energy of the particles.
Unlike an exothermic process where energy is released, sublimation absorbs heat from the surroundings to facilitate the phase change.
During sublimation, the solid particles absorb energy from their surroundings, causing the temperature of the surroundings to decrease.
This cooling effect is observed when substances like dry ice (solid carbon dioxide) or mothballs (naphthalene) sublime. As heat is absorbed, the surroundings lose energy, resulting in a decrease in temperature.
Overall, sublimation is an endothermic process because it requires the input of heat energy to break the intermolecular forces and convert a solid directly into a gas, rather than releasing heat to the surroundings.
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- Green, J. (2005). SUBLIMATION. Encyclopedia of Analytical Science, 410–415. https://doi.org/10.1016/b0-12-369397-7/00582-3
- Endothermic vs. exothermic reactions (article) | Khan Academy. (n.d.). Khan Academy. https://www.khanacademy.org/test-prep/mcat/chemical-processes/thermochemistry/a/endothermic-vs-exothermic-reactions
- Sublimation (phase transition) – Wikipedia. (2015, November 13). Sublimation (Phase Transition) – Wikipedia. https://en.wikipedia.org/wiki/Sublimation_(phase_transition)
- Sublimation – CHEMISTRY COMMUNITY. (n.d.). Sublimation – CHEMISTRY COMMUNITY. https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=72911