Which one of the following phase changes would be exothermic?
Understanding the concepts of phase changes and their energy exchanges is fundamental in the study of thermodynamics. Phase changes refer to the transitions that matter undergoes between solid, liquid, and gas states. These transitions can either be exothermic or endothermic, depending on whether they release or absorb heat. In this article, we will explore the different phase changes and determine which one would be exothermic.
Phase changes occur when the energy of a substance changes, either by absorbing or releasing heat. When a substance absorbs heat, it gains energy and transitions from a lower-energy state to a higher-energy state. Conversely, when a substance releases heat, it loses energy and transitions from a higher-energy state to a lower-energy state. Now, let’s delve into the various phase changes and identify the exothermic one.
1. Melting: This phase change occurs when a solid substance absorbs heat and transitions into a liquid state. The heat absorbed during melting is used to overcome the intermolecular forces holding the solid together. As a result, melting is an endothermic process.
2. Evaporation: When a liquid absorbs heat, it transitions into a gas state. This phase change requires energy to break the intermolecular forces between the liquid molecules. Therefore, evaporation is also an endothermic process.
3. Condensation: This phase change takes place when a gas releases heat and transitions into a liquid state. The heat released during condensation is used to form intermolecular forces between the gas molecules. Hence, condensation is an exothermic process.
4. Sublimation: Sublimation is the direct transition of a solid to a gas without passing through the liquid state. This phase change is endothermic because it requires energy to break the intermolecular forces in the solid and allow the molecules to escape into the gas phase.
5. Freezing: Freezing is the phase change in which a liquid releases heat and transitions into a solid state. The heat released during freezing is used to form intermolecular forces between the liquid molecules. Thus, freezing is an exothermic process.
In conclusion, among the listed phase changes, both condensation and freezing are exothermic processes. These phase changes release heat as the substances transition from higher-energy states to lower-energy states. Understanding these concepts is crucial in various fields, including engineering, chemistry, and environmental science, where phase changes play a significant role in energy transfer and material transformations.
